Best 9 SMTP Servers to Choose From: A Detailed Review

The best SMTP servers enhance customer engagement and trust through a reliable, secure, and efficient email delivery process.

They offer everything required for a successful email campaign, from high deliverability rates and scalable infrastructures to better security and analytics.

But with the countless options of SMTP servers available, finding the best one is akin to spotting a star in a cloudy sky — they’re there; you just need to know where to look.

We’ve filtered the options and are presenting you with the 9 best picks in this article.

Whether you’re sending WordPress emails, transactional messages, or bulk emails, these SMTP relay services are your best bet.

But before we explore the best SMTP servers, let’s take a step back and address some fundamental questions: What is SMTP, and why should you care?

Understanding SMTP Servers

While the SMTP protocol is an extensive set of rules for processing mail data, the SMTP server is the computer with software that handles the entire process. It specifically handles email submission and relaying of outgoing emails to their appropriate recipients.

Think of it as a digital post office where electronic letters are processed and dispatched to their final destinations.

Although mailbox service providers like Yahoo or Gmail offer SMTP for free, the outgoing email volume is severely limited. Therefore, businesses still need dedicated SMTP servers to send emails in bulk.

That's why we'll be reviewing the 9 best SMTP servers below.

Top SMTP Servers in 2025

Criteria for Choosing the Best SMTP Server: What to Look For

Deliverability: This refers to the percentage of emails you send that end up in the intended recipient's inbox and not the junk or spam folder. When choosing the best SMTP server for your business, look for servers with proven deliverability rates to ensure your target audience gets your emails.
Reliability: This is a server's ability to consistently deliver emails without delays or failures. To ascertain this, you need to look into the server's uptime and vital performance metrics. Server uptime is the amount of time the SMTP server is operational and accessible without outages.
Scalability: An SMTP server's scalability refers to its ability to cope with peaking volumes of email traffic efficiently. When choosing the best SMTP service provider, you must be sure of its ability to manage thousands or millions of emails per day without compromising performance.
Security Features: Choose SMTP service providers with robust security measures to protect their email infrastructure from malicious actors. This includes using secure SSL/TLS connections.
Ease of Use: Regardless of how robust the SMTP service is, it wouldn't matter if you don't know how to use it. So, look for SMTP service providers with a clear and uncomplicated setup process and an easily navigable dashboard.

How We Tested Them

We tested a long list of SMTP servers based on the criteria explained above. Our in-house experts took advantage of the free plans available and checked each service provider's deliverability rates, scalability, reliability, ease of use, and security features.

Note that besides regular SMTP services, most providers also offer sophisticated HTTP APIs for greater flexibility and speed. This extra functionality, however, incurs the complex process of integrating with your existing software. In contrast, both basic SMTP and SMTP with some extra features, often referred to as SMTP API, require just a few minutes to connect and start mailing.

To augment our findings, we also consulted user reviews of each product on review websites like TrustPilot, G2, Capterra, and Software Advice.

Best Free SMTP Servers

1. UniOne – The Most Reliable SMTP Server With Excellent Deliverability

Pros

Dedicated IP addresses: UniOne helps users build their independent sender reputation with optional dedicated IP addresses.
High deliverability rate: UniOne ensures 99.88% of all sent emails reach their destinations.
Seamless setup process: Users only need to configure the required connection settings and add a few DNS entries, which takes minutes to complete.
Comprehensive analytics features: An intuitive dashboard visualizes email campaign performance, tracks events in real time, and facilitates convenient CSV data exports.
Impressive scalability: It integrates seamlessly into existing client systems and processes up to 60 million hourly emails.
24/7 customer support: While support is available only through live chat and email, typical response time is less than 5 minutes.

Cons

CSV import restrictions: While users are mostly happy with UniOne's CSV import functions, they believe UniOne could increase its maximum limit of 32 days.
Limited email templates: Some users have reported that they would like to have more than the 40+ email templates currently offered by UniOne. An increase to 170+ templates is announced for the next update.

Pricing

Free Plan

Free trial: 4-month free trial with 6,000 emails per month and 100 email validations.

Paid Plans

Standard plans

$6/month: 10,000 emails/month
$11/month: 20,000 emails/month
$25/month: 50,000 emails/month
$40/month: 100,000 emails/month

*Pricing information retrieved from UniOne in October 2024.

Both the free and paid plan users enjoy the full set of features, including versatile Web API, integration libraries for Ruby, PHP, and C#, SPF, DKIM, and DMARC authentications for both tracking and sender domains, click and unsubscribe tracking, instant webhooks for event notification, template engines, email templates, up to 45 days of log retention, up to 400 days of analytics data storage, analytics CSV data export, 2FA, and GDPR compliance.

User Reviews

Many reviews mention UniOne’s “phenomenal” 99.8% deliverability rate, which allows users to send transactional emails reliably.

Additionally, most users are happy with the pricing compared to other services. However, despite all these compliments, some reports claim the platform can improve its aesthetics and UI features.

2. Sendgrid

Pros

Dynamic customization options: Allows users to create visually appealing email templates and personalize email content.
Seamless connection with third-party apps: Users mentioned it connects well with third-party apps like HubSpot and Apollo, thus streamlining workflows.
Robust security measures: Includes features such as authentication, encryption, SPF and DKIM validation.

Cons

30-day limit on email data retrieval: User reports indicate that Sendgrid falls behind in terms of its reporting features because it allows them to fetch data only for up to 30 days.
Expensive pricing plans: Many users believe that Sendgrid's pricing plans are not favorable for budget-conscious businesses compared to more economical alternatives.
Account deactivation issues: There have been cases of sudden account bans without explanation, raising concerns about the SMTP service provider's reliability.

Pricing

Free Plans

30-day free trial: Includes 40,000 emails
Free plan: 100 emails per day

Paid Plans

Essentials:
$19.95/month for 50,000 emails
$34.95/month for 100,000 emails

These plans include features like analytics and deliverability optimization, 1 additional teammate, 2 event webhooks, a dynamic email templates editor, reputation and delivery visibility, suppression management, universal links, etc.

Pro:
100k plan: $89.95/month for 100,000 emails
300k plan: $249/month for 300,000 emails
700K plan: $499/month for 700,000 emails
1.5M plan: $799/month for 1.5M emails

These plans include all the features of the Essential plan plus dedicated IPs, editor and testing dynamic templates, 1000 additional teammates, 5 event webhooks, 2500 email validations, single sign-on (SSO), domain authentication (SPF/DKIM), dedicated IP pooling, reverse DNS, and universal links.

*Pricing information retrieved from Sendgrid in October 2024.

User Reviews

Twilio SendGrid reviews reference its scalable infrastructure for managing fluctuating email volumes without sacrificing efficiency. Additionally, its wide range of email template customization choices facilitates creating aesthetically pleasing and highly customized emails.

However, according to some users, even though the platform has many functions, the initial setup procedure can be difficult for beginners. More user-friendly knowledge base would be helpful. Nonetheless, its positive reviews for reliability and functionality have earned it a spot on our list of best SMTP providers.

3. Mailgun

Pros

Reliable email tracking capabilities: For monitoring email performance easily.
Comprehensive documentation: Well-structured API documentation makes implementation easy for developers.
Powerful APIs and webhooks: Facilitating seamless integration and management of email tasks.

Cons

Inconsistent customer support: There have been multiple user complaints about slow response times and unhelpful customer support interactions.
Time zone limitations: Users in the EU timezone feel Mailgun could do better by having customer support staff work in their timezone, while most support infrastructure is currently in the US timezone.
Pricing: Some users say the pricing structure is less economical for businesses with a high volume, and higher-tier subscription is mandatory for full capabilities.
Technical Problems with UI Updates: Users have complained that updates to the user interface are confusing because they don't always show up right away on the backend.

Pricing

Free Plans

30-day free trial on all pricing tiers: unlimited access to the corresponding plan's features (credit card required)
Free plan: up to 100 emails/day

The free plan includes features like ticket support, RESTful email APIs and SMTP relay, 1 custom sending domain, 1 API key, email analytics and reporting, 1-day log retention, and 1 inbound route.

Paid Plans

Basic plan

Basic 10K plan: $15/month for 10,000 emails.

The basic plan includes no daily email limit, monthly email overage options, RESTful email APIs and SMTP relay, 1 custom sending domain, 1 API key, email analytics and reporting, 1-day log retention, and 1 inbound route.

Foundation plan

Foundation 50K plan: $35/month for 50,000 emails.
Foundation 100K plan: $75/month for 100,000 emails
The foundation plans include everything on Basic plus 1,000 custom sending domains, 5 days log retention, 1-day message retention, and full access to inbound routing

Scale plan

Scale 100K plan: $90/month for 100,000 emails.
Scale 500K plan: $400/month for 500,000 emails.
Scale 1M plan: $700/month for 1,000,000 emails.
Scale 2.5M plan: $1,250/month for 2,500,000 emails.

*Pricing information retrieved from Mailgun in October 2024.

User Reviews

When handling transactional emails and email marketing efforts, many value Mailgun’s user-friendliness and dependable delivery. In addition, most users claim to have found its thorough documentation particularly helpful.

However, some users do think that Mailgun's customer service could be better. Since Synch's acquisition, reviews have shown a drop in service quality, with a few reports of support staff members giving generic responses and poor response times when problems occur. This has left some users feeling stuck.

4. Postmark

Pros

Intuitive user interface: Users find it easy to navigate and utilize Postmark's SMTP services due to its user-friendly interface.
Easy integration: Postmark offers an extensive set of libraries for most programming languages.
Content-ready email templates: Many users appreciate that Postmark's email templates are responsive and look great in most email clients.

Cons

High pricing for low volumes: Compared to other SMTP providers offering a per-email pricing plan, Postmark may not be as competitive for users with low email volumes. For instance, while UniOne charges $6 per month for 10,000 emails, Postmark charges more than double that at $15 a month for the same amount of emails.
Limited training resources: New users claim to struggle to understand the platform due to the minimal training resources available.
Few analytics features: The provided email performance analytics reports could be more detailed.

Pricing

Free Plans

Free trial: 100 free emails/month
Free developer plan: 100 emails/month

Postmark's free plan also doubles as a free trial to all paid plans.

Paid Plans

$15/month: 10,000 emails
$55/month: 50,000 emails
$115/month: 125,000 emails
$245/month: 300,000 emails
$455/month: 700,000 emails
Custom plan: 1,900,000+ emails/month

*Pricing information retrieved from Postmark in October 2024.

All postmark plans (no matter free or paid) guarantee access to all the platform’s features. These include API and SMTP sending, SMTP, REST API, third-party integrations, spam score checking, separate environments with servers, pre-made email templates, and a template engine.

User Reviews

Postmark supports TLS to secure user data and client-server connections. Many users have found that Postmark critically helps them improve the delivery of important emails.

However, some reviews claim Postmark could improve its analytics features for better email performance evaluations. Additionally, there are requests for more thorough training materials to help new users navigate the platform efficiently, even though support is usually responsive.

5. SMTP2GO

Pros

Visual reports: Comprehensive reporting about email bounces, unsubscribes, spam complaints, etc., to help users understand what is actually happening with every email sent.
Customizable account configurations: This feature helps users set separate limitations and configuration settings for different sub-accounts, thus catering to diverse business needs.
Advanced email testing features: Users get to see how their emails appear in over 40 different email clients before sending them.

Cons

Log search limitations: Some users find it difficult to search their logs because they can't convert the date and time to their local timezone.
Payment processing difficulties: There have been reports of difficulties with billings and payments.
Complex DNS settings for multiple domains: Users with many sender addresses have reported difficulties managing DNS settings.

Pricing

Free Plan: Includes 1,000 emails a month with a cap of 200 emails per day

Includes 5 days of email reporting and ticket support in addition to the all-inclusive features for all plans. These are automatic DKIM/SPF, feedback loops, blacklist monitoring, spamtrap detection, real-time analytics, bounce tracking, unsubscribes, weekly summaries, best-path routing, redundancy built-in, TLS/SSL security.

Paid Plans

Starter plans

$15/month: 10,000 emails
$30/month: 50,000 emails

Includes 30 days of email reporting, ticket/chat/phone support, sub-account management, SMS messaging, and scheduled reporting.

Professional Plans

$75/month: 100,000 emails
$170/month: 250,000 emails
$280/month: 500,000 emails
$520/month: 1,000,000 emails

It includes all Starter plan features plus a dedicated IP address and email testing tools.

Custom plans

For over 3,000,000 emails per month, with all the features available in the Professional plan.

*Pricing information retrieved from SMTP2GO in October 2024.

User Review

Many SMTP2GO users have outlined its ease of use and distributed data center infrastructure as standout features. The email delivery solution also offers robust reporting tools that enable users to keep their email lists updated.

However, some user reviews have shown that SMTP2GO falls behind when it comes to processing incoming emails effectively. Additionally, SMTP2GO occasionally displays issues with the spam blocking, according to some user reviews.

6. Mailjet

Pros

Advanced automation and segmentation: Users can personalize campaigns and segment their audience according to their digital marketing strategy.
Integration capabilities: Mailjet's API allows seamless integration with multiple CRM systems.
User-friendly interface: The intuitive design makes it easy to create and manage email campaigns without extensive technical skills.

Cons

Customer support improvements needed: Some users believe Mailjet's customer support team could improve its efficiency in resolving queries.
Inconsistent analytics: There are calls for more detailed analytics to provide deeper insights into email performance.
Limited template customizations: The available template options could be more flexible.

Pricing

Free Plans

Free Premium trial: 30 days
Free plan forever: 6000 emails per month with 200 emails daily

The Free plan includes 1500 Contacts, APIs, SMTP relay, webhooks, an advanced email editor, basic statistics, and a form builder.

The free Premium plan includes all the features listed in the paid Premium plan below.

Paid Plans

Essentials (no daily sending limit)

$17/month for 15,000 emails
$37/month for 50,000 emails

Includes all Free plan features plus unlimited contacts, online customer support, no Mailjet logo, 500 email previews per month, 500 email address validations, segmentation, 1 subaccount, AI copy generator, and AI subject line generator.

Premium (no daily sending limit)

$27/month for 15,000 emails
$55/month for 50,000 emails
$105/month for 100,000 emails
$470/month for 500,000 emails

Includes all Essential plan features, plus advanced statistics, priority support, chat and phone support (for 50k+ plans), 1 dedicated IP (for 100k+ plans), 2000 email address validations included (for 100k+ plans), and single sign-on (SSO) (for 100k+ plans).

Custom plan

This includes all Premium plan features, plus a dedicated technical account manager, comprehensive onboarding, strategic deliverability consulting, and training.

*Pricing information retrieved from Mailjet in October 2024.

User Reviews

Mailjet’s ease of use allows users with limited technical knowledge to create effective email campaigns quickly. Free pricing offerings are another offering highly appreciated by most users.

However, users suggest that Mailjet could improve its template customization options. They find the available designs somewhat limiting compared to other top SMTP providers.

7. iDealSMTP

Pros

Reporting features: Offers a dashboard that tracks sent emails for monitoring campaign performance.
Dedicated email server: Provides better control and security features for email marketing operations.
User-friendly interface: The platform makes it easy to set up and manage email campaigns.

Cons

Email deliverability issues: Although some users reported email deliverability success, many others have complained about emails not reaching the intended recipients.
Limited responses to refund requests: In response to initial issues, some users have claimed that they couldn't get a refund after requesting for one.
IP reputation concerns: There have been problems with the reputation of the assigned IP addresses for sending emails.

Pricing

Free Plan

No free plan offered

Paid Plans

Trial SMTP plan: $50 for 3 days

Standard SMTP plan: $145/month

Premium SMTP plan: $225/month

Professional SMTP plan: $350/month

Cluster SMTP plan

*Pricing information retrieved from iDealSMTP in October 2024.

User Review

Some iDealSMTP users believe the platform to be user-friendly and value how easy it was to create campaigns. Furthermore, they noted that their affiliate links were clicked on within the first few days of sending, indicating early success with email delivery and engagement metrics.

On the other hand, some users claim the platform lags behind competitors in terms of email deliverability. They couldn't find proof that recipients were getting the emails or reacting to the content, even though the dashboard showed that they had been delivered.

8. Amazon SES

Pros

Cost-effectiveness: Many users find the Amazon SES pricing model very affordable.
Integration capabilities: It easily integrates with many third-party tools and applications.
Reliable performance: Backed by Amazon's robust infrastructure, Amazon SES ensures consistent email delivery and uptime.

Cons

Cumbersome setup process: Users often find the initial setup process to be quite challenging, requiring a solid technical understanding of AWS and email protocols.
Tedious authentication setup: Setting up authentication mechanisms like SPF and DKIM can be cumbersome.
Limited email marketing features: Amazon SES falls behind in terms of advanced marketing functionalities like A/B testing and built-in templates.

Pricing

Free Plans

AWS Free Tier: 3000 message charges per month for 12 months

Includes outbound emails, inbound emails, and virtual deliverability manager outbound email processing.

Paid Plans

Amazon SES offers a pay-as-you-go pricing model based on the volume of emails sent and received. As such, the features are priced as follows:

Outbound email: $0.10 per 1000 emails
Inbound email: $0.10 per 1000 emails
Mail manager:

Open ingress endpoint: $50 per month per endpoint
Email processing: $0.15 per 1000 emails
Archiving:

$2 per GB of emails ingested
$0.19 per GB per month for searching and storing the archive

Email add-ons: prices vary based on the chosen add-on solution

*Pricing information retrieved from Amazon SES in October 2024.

User Reviews

Users appreciate Amazon SES’s cost-effectiveness and comprehensive integration capabilities. They claim it helps them streamline their email operations effectively. Furthermore, the cloud-based email service provider supports various deployments, such as dedicated, shared, or owned IP addresses. It also provides sender statistics that help outreach experts make every email count.

However, some users suggest that Amazon SES could improve its setup process, as many find it complex and requiring substantial technical knowledge. Multiple complaints mentioning limited customer support, which hinders timely issue resolution, have also been recorded.

9. Mailtrap

Pros

Strong Analytics and Alerts: The platform offers in-depth analytics and alert features that help users monitor email deliverability and performance effectively.
User-Friendly Experience: Many users find the interface intuitive and accessible even for non-technical team members.
Responsive Customer Support: Users consistently highlight the helpfulness and quick responses of the support team, enhancing the overall experience.

Cons

Domain Verification Speed: Reports suggest the speed of domain verification processes needs to be increased to improve user experience.
Limited Bulk Email Capabilities: Users note that Mailtrap is currently not equipped to handle peak volumes well, which could be a limitation for some businesses.
Need for More Integrations: Users would like to see more ready-made integrations with popular CRMs and e-commerce platforms.

Pricing

Free Plans

Free Forever: 1000 emails per month and 500 contacts

Paid Plans

Basic plans

$15/month: 10,000 emails/month and 2,500 contacts
$30/month: 100,000 emails/month and 25,000 contacts

Business plans

$85/month: 100,000 emails/month and 25,000 contacts
$200/month: 250,000 emails/month and 62,500 contacts
$450/month: 750,000 emails/month and 187,500 contacts

Enterprise plans

$750/month: 1,500,000 emails/month and 375,000 contacts
$2,000/month: 5,000,000 emails/month and 1,250,000 contacts

Custom plans

Tailored for high-volume senders and agencies with 5+ sub-accounts

*Pricing information retrieved from Mailtrap in October 2024.

User Reviews

Mailtrap is generally favored by users, who especially value its development into a feature-rich email-sending platform. Thanks to its friendly interface, which is often cited as a major asset, teams with different technical skill levels may effectively utilize the platform.

However, users think that Mailtrap might improve its services by adding more email marketing features. These days, many people have to use different platforms for their marketing requirements, which might make processes more difficult. Furthermore, despite the API's strength, several users initially had trouble understanding it, suggesting that tutorials or documentation could be improved.

Frequently Asked Questions

Which SMTP service provider is the best?

Some of the best SMTP servers include UniOne, Sendgrid, Mailgun, Postmark, SMTP2GO, Mailjet, iDealSMTP, Amazon SES, and Mailtrap.

Should I use port 587 or 25 for SMTP connection?

While port 25 was the original port number used as a default port for SMTP, port 587 has emerged as the most appropriate port because it is used for SMTP Secure (SMTPS) encrypted email transmission.

What is the name for Gmail's SMTP server?

The default Gmail SMTP server name is smtp.gmail.com.

Final Takeaway

Choosing the best SMTP server for your email campaign is essential in 2024 to guarantee dependable email delivery and successful marketing campaigns. High deliverability rates, comprehensive analytics, intuitive user interfaces, and first-rate customer service are just a few of the benefits that the top SMTP services provide.

As highlighted in our review, factors such as email volume, budget constraints, and level of technical expertise should primarily guide your choice.

Before choosing an SMTP provider, spend some time evaluating your unique needs and determining how various providers meet them. This will enhance your operations and ensure that your messages reach their intended recipients reliably and effectively.