Every one of these services will deliver your password resets. That's not the differentiator.
What differs is setup difficulty, what the free tier covers, how good the logs are when something goes wrong, and — the one people never consider until it bites them — whether the service also handles marketing mail, and whether you actually want it to.
Here's how they compare on what matters for a WordPress site.
The short version
| Service | Best for | Setup | Marketing too? |
|---|---|---|---|
| Postmark | Sites where receipts must arrive | Easy | No — transactional only |
| Brevo | Small sites wanting one tool | Easy | Yes |
| Mailgun | Developers, moderate volume | Moderate | Limited |
| SendGrid | General purpose, scale | Moderate | Yes |
| Amazon SES | High volume, technical teams | Hard | Yes |
For most WordPress sites: Postmark if transactional delivery is critical and you're happy keeping marketing separate. Brevo if you want one account for both and value simplicity.
What to judge them on
Five things, in order of what actually matters for a WordPress site.
Deliverability track record. All are competent. The meaningful difference is how tightly each polices its shared IP pools — a service that tolerates spammers on shared infrastructure passes that reputation to you. Hard to assess from outside, which is why the transactional-only providers have an edge here.
Setup difficulty. How long from signup to working mail. Matters more than people admit, because a service you configure incorrectly delivers worse than a simpler one configured properly.
Logging quality. When a customer says they never got their receipt, can you see what happened? Retention length matters too.
Free tier. Most small WordPress sites fit comfortably inside one.
Whether it handles marketing. Genuinely a strategic question, not a convenience one — see below.
Postmark — for receipts that must arrive
Postmark is transactional-only by policy. You cannot send marketing mail through it, and it will close your account if you try.
That sounds like a limitation and is the main reason to choose it. It means the shared infrastructure carries only transactional mail — receipts, resets, notifications — which is the highest-reputation category of email there is. No promotional campaigns from other customers, no complaint-generating blasts sharing your IP pool.
Setup: among the easiest. Servers → Signatures/Domains, publish the DNS records.
Logging: generally considered the best in class, with a searchable activity log showing full message content and delivery events. When you need to prove what was sent, this is the one you want.
Watch for: it's a paid service with a limited free allowance. And the policy is enforced — if you want to send a newsletter, you need a second service.
Best for: stores, membership sites, SaaS, anything where a missed transactional email costs money.
Brevo — for small sites wanting one tool
Brevo (formerly Sendinblue) handles both transactional and marketing mail from one account.
Setup: straightforward, with a well-supported WordPress plugin and API-based configuration.
The appeal: one account, one dashboard, one set of DNS records. For a small business sending order confirmations and a monthly newsletter, that's genuinely simpler than running two services.
Watch for: the convenience is also the risk. Sending both streams through one account means your marketing behaviour and your transactional reputation are entangled. Use separate subdomains for each stream even within one provider — most services support this, and it's the point of the domain architecture below.
Best for: small businesses that want one tool and won't manage two.
Mailgun — for developers
Developer-focused infrastructure with a strong API and good documentation.
Setup: moderate. Sending → Domains, then DNS records. More technical framing than Postmark or Brevo.
Watch for: oriented toward developers rather than site owners, so the dashboard assumes more knowledge. Marketing capability exists but isn't the focus.
Best for: sites with developer involvement, or moderate volume where the API matters.
SendGrid — general purpose at scale
The most widely used of the group, handling both transactional and marketing.
Setup: moderate. Settings → Sender Authentication → Authenticate Your Domain.
Watch for: its scale means very large shared IP pools with a wide range of senders. That's a reputation consideration — you're sharing infrastructure with a lot of other people's behaviour, and you have limited visibility into it.
Best for: larger sites, or teams already using it elsewhere.
Amazon SES — cheapest at volume, hardest to set up
Sending infrastructure rather than a product. Extremely cheap at scale, and it assumes you know what you're doing.
Setup: the hardest here. Verified identities → create identity → Easy DKIM, plus AWS account configuration, region selection, and getting out of the sandbox.
The sandbox catches everyone. New SES accounts can only send to verified addresses until you request production access. People configure everything correctly, test to their own address successfully, go live, and discover nothing reaches customers.
Watch for: nothing is automated. You own warm-up, suppression logic, and monitoring your account-level reputation dashboard. Exceed the bounce or complaint thresholds and AWS will pause your sending.
Best for: high volume with technical resources. Overkill for a site sending a few hundred emails a month.
Which has the best free tier?
Most of these offer free tiers that comfortably cover a typical small WordPress site's transactional volume.
I'm deliberately not quoting the numbers. Free-tier limits change frequently — several of these services have revised theirs in the last couple of years — and a stale figure here would send you to the wrong provider.
Check current limits directly, and when you do, check three things beyond the headline number:
Is it a monthly allowance or a trial period? Some "free tiers" expire.
What's the log retention? A free tier with three days of logs is much less useful than one with thirty.
What happens when you exceed it? Some throttle, some queue, some stop. Worth knowing before it happens mid-launch.
Can you use one service for both?
Technically yes. Strategically, be careful.
The problem: providers score reputation per domain and subdomain. Marketing mail generates complaints and unsubscribes even when done well. Transactional mail — receipts and resets — is genuinely wanted and has near-100% open rates, making it your strongest reputation asset.
Mix them and one bad campaign can damage the reputation your invoices depend on. There's a subtler trap too: if someone unsubscribes from marketing but keeps receiving mixed-stream mail from the same address, providers can read that as ignoring the unsubscribe.
The architecture that works, regardless of provider count:
| Stream | Domain |
|---|---|
| Human / corporate | yourbrand.com |
| Marketing | news.yourbrand.com |
| Transactional | notify.yourbrand.com |
Each subdomain needs its own complete SPF, DKIM, and DMARC setup, and builds its own reputation while inheriting brand recognition from the root.
The honest caveat: subdomain separation contains damage but isn't a firewall. Providers still consider the root domain's overall behaviour. It reduces blast radius; it doesn't grant immunity.
So the practical answer: one service is fine if you use separate subdomains for each stream. Two services — one transactional-only, one for marketing — is cleaner and is what Postmark's policy effectively enforces.
Migrating between them
If you're switching:
Authenticate the new service on your domain first, adding its include: to your existing SPF record rather than creating a second one — and watch the 10-lookup limit.
Test thoroughly before switching over. Password reset, test order, form submission, to at least two different providers.
If you're moving to a new subdomain, warm it. A brand-new sending domain has zero reputation, and "new plus sudden volume" is the classic spam fingerprint. Ramp gradually.
Leave the old DKIM key published for a couple of weeks so mail still in flight verifies.
Frequently asked questions
Which has the best free tier?
Most of these offer free tiers that comfortably cover a typical small WordPress site's transactional volume, but the limits change frequently enough that any figure quoted in an article goes stale. Check each provider's current limits directly, and look beyond the headline number at three things: whether it's a monthly allowance or an expiring trial, how long logs are retained, and what happens when you exceed it — throttling, queuing, and hard stops are very different outcomes mid-launch.
Is Amazon SES worth the setup?
Only at genuine volume with technical resources available. SES is dramatically cheaper at scale, but nothing is automated — you own warm-up, suppression logic, and monitoring your account-level reputation. The sandbox catches almost everyone: new accounts can only send to verified addresses until you request production access, so people test successfully to their own address, go live, and discover nothing reaches customers. For a site sending a few hundred emails a month, a simpler service is the better trade.
Can I use one service for both marketing and transactional?
Technically yes, and it's fine if you use separate subdomains for each stream. The risk in mixing them on one domain is that providers score reputation per domain and subdomain, so a bad promotional campaign can damage the reputation your order confirmations depend on. Two services — one transactional-only like Postmark, one for marketing — is cleaner, which is effectively what Postmark's transactional-only policy enforces.
What to do next
Start with a question rather than a comparison: if an order confirmation didn't arrive, how much would that cost you?
High — a store, a membership site, anything where people pay before the email — go with a transactional-only service and keep marketing entirely separate. The policy that seems restrictive is the feature.
Low — a brochure site with a contact form — pick whichever has the simplest setup and a free tier that fits. You'll spend more time configuring it than you'll ever spend thinking about it again.
Free: The 60-Minute Email Authentication Fix.
Go deeper: The Email Deliverability Playbook — the full domain architecture model and provider-by-provider authentication paths.
Related guides
- How to set up SMTP in WordPress — connecting whichever you choose
- WordPress emails not sending — the wider problem
- Which email service actually delivers? — the marketing-side equivalent
- Email authentication — the records each service needs
Join the Newsletter
Get practical marketing tactics delivered straight to your inbox.
Written by
Muhammad Basim
Related Articles
Contact Form Notifications Not Arriving: Every Cause
Here's the version of this problem that costs the most: it's been happening for months and you don't know. The form says "thank you." The visitor believes they've reached you. You believe nobody's been in touch. There's no error, no bounce, no alert — just an absence, and absences are invisible. Most of the time […]
WooCommerce Order Emails Going to Spam: The Fix
"I never got a confirmation. Did my order go through?" Every store owner gets this message. And when it arrives often enough, you stop treating it as customer confusion and start realising your receipts genuinely aren't landing. This costs more than most email problems, because a missing order confirmation doesn't just annoy someone — it […]
How to Set Up SMTP in WordPress, Step by Step
Twenty minutes, once, and your site's email stops being a mystery. The job is simple in principle: stop WordPress handing mail to your web server, and hand it to a service that exists to send mail properly. What follows is the actual sequence, including the two steps people skip that make the difference between "the […]