The Top 5 Transactional Email Services for Developers

When a transactional email fails to reach the inbox, or gets delayed, the failure often translates to poor UX (user experience), lost revenue, or could even point to a security risk. 

Therefore, choosing a reliable Email Service Provider (ESP) is more than just choosing an affordable provider with a nice feature set. It’s an infrastructure decision that requires dev teams to assess the API robustness, software performance, and deliverability features. 

This write up does most of the heavy lifting for you to help you make a more informed choice. 

Developer checklist for high-performance ESPs

If your platform needs to check tens of thousands of emails every day, system stability is everything. And here’s how to check if an ESP is indeed stable. 

1. API architecture and integration: The ESP of your choice needs to have a RESTful API that’s flexible and well-documented. At the very least, it has to provide programmatic sending (with a certain level of automation), webhook integration, and email template management. It’s also really helpful if the provider offers official SDKs for popular languages. 
2. Deliverability and inbox placement: Authentications and DNS management are non-negotiable. And if you send at a volume, you need a platform with strict IP management and security protocols, as well as preemptive abuse handling at the domain verification level. 
3. Performance monitoring and observability: It’s impossible to fix what you cannot measure. Following that logic, developers need the industry-best analytics that granulates to mailbox providers, email categories, send times, etc. This level of observability is necessary to troubleshoot bottlenecks and identify trends that could affect your deliverability. 
4. Stability and support: Even with the best of providers, sudden deliverability issues may happen. For instance, if you experience a sudden block from a major ISP, you need an expert right away. So, the transactional email service providers have to offer 24/7 support with deliverability experts on hold, not just customer service agents. 

Best transactional email services for high-volume senders

We evaluated a number of services based on deliverability performance, API flexibility and observability. Here are the top five contenders for you to consider. 

1. Mailtrap Email Delivery Platform

Mailtrap is an Email Delivery Platform for developer and product teams with high inboxing rates and fast email delivery. 

They went so far to run GlockApps tests showing that 93.2% of emails get delivered with only 5.8% going to tabs instead of the inbox.

Key features: 

• API/SMTP: You get a flexible, well-documented RESTful API with official SDKs for major languages, including ready-made integration examples. 
• High inboxing rates: Check the screenshot above for SMTP results with the standard GlockApps seed list without an IP warmup. 
• Industry-best analytics: Mailtrap provides a helicopter-view dashboard with drill down reports you can access in one click. 
• 24/7 tech support: Starting from the Business plan, you have access to 24/7 support (live chat included), deliverability expert assistance, and migration assistance. 

Now you may wonder about the Mailtrap shortcomings. The main one is that automations for promotional campaigns are still in beta. But using API, you can set up triggers for transactional emails without any hustle.  

2. SendGrid

SendGrid is a mature platform and its appeal lies in scalability (SendGrid can handle millions of emails without hiccups) and API documentation. The platform also offers quite comprehensive metrics and reporting, though it could be a bit overwhelming for teams who don’t have experience with email infrastructure. 

Key features:

• API/SMTP: Both options are available and well-documented. 
• Analytics: As mentioned, SendGrid has comprehensive analytics, but some deliverability insights could actually be integrated with marketing features. 
• Scale: SendGrid has a proven track record of handling massive volumes reliably. 

 3. Postmark

Two key aspects put Postmark on this list - they focus on transactional emails (though they offer bulk as well) and fast delivery times. In addition, the service has built a reputation for high deliverability, mostly due to strict sender acceptance criteria, but they also have separate transactional and bulk sending streams. 

Key features: 

• API/SMTP: Clean, developer-friendly API with a focus on simplicity. 
• Analytics: Detailed logging and statistics primarily tailored to transactional emails. 
• Limitations: Postmark can be restrictive on the types of sending content. This could limit the cases with emails that kinda blur the line between transactional and low volume bulk. This may happen with feature upgrades and specific feature-based product announcements. 

4. Amazon SES

Amazon Simple Email Service (SES) works best for engineers who already work within the AWS environment. It’s among the most affordable platforms, but that’s compensated for with a highly dev-centric interface, setup, and integrations. In simple English, you need to be an experienced engineer to set up and use SES properly. 

The good news is that scalability and reliability of SES is hard to rival if you’re comfortable with limited native analytics. 

Key features: 

• API/SMTP: API interaction is native to AWS SDKs. That makes for a complex setup for non-AWS projects, though there’s also a handful of community libraries you can work off of. 
• Deliverability: As said, it requires a lot of manual setup for DNS configurations and dedicated IPs. It translates to moving your deliverability management entirely in-house, which can be a pain. 
• Support: You get the standard AWS support models, meaning you need a higher tier package for expert consultations. 

5. Mailgun

Developers like Mailgun because of its simple (but not simplistic) syntax and the emphasis on inbound parsing and email processing. This is one of the reasons the service is popular for applications that handle command-line email utilities and replies. 

Key features: 

• API/SMTP: Solid REST API and SMTP with straightforward initial setup.
• Validation tools: The tools simplify post-send logging and pre-send email checks. 
• Deliverability management: To keep top-tier inboxing rates your development team needs to actively monitor the infrastructure and system responses. 

Conclusion

At the end of the day, as a developer, your choice narrows down to the services that offer:

• RESTful API performance
• Granular analytics dashboards 
• Guaranteed access to deliverability experts 

And if you focus on providers like Mailtrap, who prioritize core deliverability features, high inboxing rates, and 24/7 expert support, you’re building the stability that translates to superior user experience.