Pick Postmark if you only need dependable application email, with message streams to keep traffic apart and 45 days of searchable history by default. Pick SendGrid if you want an email API and marketing campaigns in one account, or you already run SMS or voice on Twilio. Neither proves better delivery, so test both with your own sending domain.
A password reset that arrives ten minutes late is a support ticket. One that never arrives is a lost customer. That's the job both of these services are hired for, and it's why the choice between them deserves more thought than picking whichever name a developer has heard of first.
For readability I'll call Postmark the app-mail specialist and SendGrid the Twilio email API, because ownership turns out to matter here more than you'd expect.
Short advice before the detail
If your product sends receipts, resets and alerts and little else, the app-mail specialist is the cleaner fit: it pitches application email only, separates traffic with message streams and keeps a long default history for chasing lost messages. If you want transactional sending and marketing campaigns under one login, or your team already uses Twilio for texts or calls, the Twilio email API makes more sense. Neither site proves better inbox placement, so send real mail from your own domain through both before you commit.
Who owns each one now
Neither is an independent company any more. The specialist's footer says it's made at ActiveCampaign, the marketing automation company. The other's website now tells visitors it has merged into Twilio.com, where email sits next to SMS, WhatsApp, voice and customer data products.
So you're choosing between a narrow email product inside a marketing automation business and an email API inside a large communications platform. That isn't good or bad on its own. It does change who you'll be dealing with when you need help, and where the product's roadmap is likely to point.
One more thing worth knowing: the specialist runs a comparison page against its rival on its own site. Read it if you like, but treat it as marketing, because that's its job.
Keeping app mail apart from newsletters
Mixing a marketing blast with password resets on the same sending setup is a classic way to hurt the email that matters most. The two services handle that split differently.
The specialist has a named feature for it: Message Streams, which separate types of email traffic. It also offers a separate Bulk API for larger sends, while keeping its main pitch firmly on transactional mail.
The Twilio email API splits things at product level instead. Its Email API covers sending at scale through an API or SMTP, and Marketing Campaigns is a separate product for marketers. If your marketing team wants its own tool and your developers want theirs, but you'd like one vendor for both, that structure suits you.
The pair in one grid
| What you're weighing | Postmark | SendGrid |
|---|---|---|
| Main focus | Application email only, plus a separate Bulk API | Email API and SMTP, plus Marketing Campaigns |
| Owner | Made at ActiveCampaign | Website merged into Twilio.com |
| Separating traffic | Message Streams | Separate API and campaign products |
| Message history | 45 days of full content, recipients and events by default, adjustable | Deliverability insights and advanced analytics; no default history length stated |
| Support | Says great support never comes as an extra; publishes a customer happiness rating | Expert support, dedicated IPs, an AI assistant in the Help Center, support plans listed |
| Scale claim | Billions of emails delivered since 2010 | 200+ billion emails every month; names Shopify and Nextdoor |
| Getting started | Free trial stated | Free trial stated |
Chasing a message that went missing
When a customer says they didn't get their receipt, someone has to find out why. The specialist keeps 45 days of full content history, recipient information and message events by default, and you can change that retention. For a support team, that means you can look up the exact message and see what happened to it weeks later.
The Twilio email API talks about deliverability insights and advanced analytics, which helps when you're spotting trends across huge volumes. Its site doesn't state a default history length, so if search-back time matters to you, ask before you sign up.
Support promises and scale claims
The specialist states that great support never comes as an extra, and it publishes a customer happiness rating. The Twilio side mentions expert support and dedicated IPs, has an AI assistant in its Help Center, and lists support plans in the Twilio footer. Read that as support coming in tiers, and find out which tier you'd be on.
On scale, the gap in claims is huge. The specialist says it's delivered billions of emails since 2010. The other says it delivers more than 200 billion emails every month and names Shopify and Nextdoor as customers. Big volume is reassuring, but it doesn't tell you how your own mail will land, which depends a lot on your domain and your sending habits. If the move into Twilio has you rethinking things, here's a rundown of other email APIs worth a look.
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Five questions to answer before you switch
- Do you send anything besides transactional email? If marketing mail matters too, a single account with campaigns may save you a second vendor.
- Are you already on Twilio for SMS or voice? Keeping email in the same place may simplify your setup.
- How far back does support need to search? 45 days by default is a clear answer on one side.
- Who'll answer when mail stops going out? Check whether support comes in tiers, and which one you're on.
- Have you sent real mail from your own domain through both? Neither site proves better delivery, so that's the check that counts.
Other sending services on the shortlist
These four are the closest alternatives. For a longer list, our guide to the best email APIs for developers compares more of them.
Mailgun
Best for: Developers who want an email API and SMTP relay with validation, inbox placement testing and deliverability tools built in.
Amazon SES
Best for: Teams already on AWS that want infrastructure-style sending for transactional, marketing and bulk mail, with shared, dedicated or owned IPs.
Resend
Best for: Modern JavaScript and app developers who like a developer-first API, SDKs in many languages and React Email components.
Mailjet
Best for: Mixing newsletters with transactional sending: an editor, automation and segmentation sit next to an Email API and SMTP relay.
Do you make an email API or delivery service? Tool makers can ask to be considered for a featured place on this page.
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Frequently asked questions
Is SendGrid part of Twilio now?
Yes. Its website says it has merged into Twilio.com, where email sits alongside SMS, WhatsApp, voice and customer data products.
Who owns Postmark?
Its site footer says it's made at ActiveCampaign, the marketing automation company.
Which keeps email history longer?
The app-mail specialist keeps 45 days of full content, recipients and events by default, and lets you change it. The Twilio email API doesn't state a default history length.
Can I send marketing emails with either?
The Twilio email API has a separate Marketing Campaigns product. The specialist focuses on application email, with a Bulk API for larger sends.
Which one has better deliverability?
Neither site proves better delivery than the other. Send real mail from your own domain through both and compare where it lands.
