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MailerSend plugin for WordPress

Last reviewed/updated:

Install the official MailerSend SMTP integration if the site has already settled on MailerSend and wants a single-purpose plugin that does one thing. Install WP Mail SMTP or FluentSMTP in Other SMTP mode if the site benefits from plugin-side logging, fallback, or per-sender routing on top of MailerSend’s dashboard. Both paths reach smtp.mailersend.net:587 with the same SMTP credential pair; the choice is about what the plugin does around the send, not about how the send itself works.

For the case for or against MailerSend as the sending service (the 500-a-month free tier with vendor branding, the $7 Hobby tier for small sites, the crossover with SMTP2GO at the low end), start at the MailerSend review. This page is the setup walk-through. It assumes the decision to use MailerSend has already been made.

Which plugin to install

Four plugins reach MailerSend, and the choice comes down to whether the operator wants a minimal, MailerSend-only integration or a general-purpose mailer plugin with logging and routing.

MailerSend Official SMTP Integration is the vendor’s own plugin, published by MailerSend and last tested against WordPress 6.9. It exposes one settings screen: paste the SMTP username, paste the password, set the from-address, save. The plugin does not ship email logging, fallback, or routing – it hands the send off to smtp.mailersend.net and returns whatever the SMTP server said. Pick it when MailerSend is the final decision, when a second mailer plugin’s feature set is not needed, and when the operator prefers the smallest possible install on the WordPress side.

WP Mail SMTP does not have a dedicated MailerSend mailer in its picker, but its Other SMTP option connects to smtp.mailersend.net:587 with the same credentials as the official plugin, and adds the surrounding features MailerSend’s own plugin omits: email logging (free), a setup wizard, and, on the Pro tier, backup connections and smart routing. Pick it when the site might change providers later, or when the operator wants the full mailer-plugin feature set from day one.

FluentSMTP reaches MailerSend in generic-SMTP mode on smtp.mailersend.net:587. FluentSMTP is free and open-source with no upsell path, and its per-address routing rules are cleaner than WP Mail SMTP’s free tier. Pick it when the site runs multiple senders and needs per-address routing without paying for WP Mail SMTP Pro.

Post SMTP reaches MailerSend in generic-SMTP mode with the same credentials. Its differentiator is real-time failure notifications (Chrome push, Slack, Teams, and SMS on the paid tier); if a bounced order confirmation needs to page an operator within minutes, Post SMTP is the plugin.

For the plugin-by-plugin comparison in the general case (not MailerSend-specific), see best WordPress SMTP plugins.

Before touching WordPress

MailerSend will not accept a send from a domain until the domain is added, verified, and its DKIM records propagate. Two things sit upstream of the WordPress install: a verified sending domain, and SMTP credentials generated inside MailerSend’s dashboard.

Verify the sending domain and publish DKIM and SPF

Log in to the MailerSend dashboard, then Email > Domains > Add a domain. Enter the domain the WordPress site sends From:, meaning example.com, not mail.example.com. MailerSend returns the DNS records to publish: two DKIM CNAME records under ms1._domainkey.<your-domain> and ms2._domainkey.<your-domain> pointing at MailerSend’s key servers, one CNAME at mta.<your-domain> pointing at mailersend.net for the return path, an SPF entry to add, and an optional custom tracking CNAME if the site wants tracked links to resolve under its own subdomain.

The SPF entry adds include:_spf.mailersend.net to the domain’s existing SPF record at the apex. If the domain already has an SPF record covering Google Workspace or another sender, edit it to add the include; do not create a second SPF record at the apex, because a domain with two SPF records at the same name is a permanent SPF error under RFC 7208 regardless of what the records say. If the domain has no SPF record, publish v=spf1 include:_spf.mailersend.net -all. The SPF merger folds the MailerSend include into an existing string and counts the DNS lookups against RFC 7208’s ten-lookup ceiling before you publish.

Return to the MailerSend dashboard and click Verify. Verification is typically minutes when propagation is fast and up to an hour on slow DNS hosts. The dashboard reports each record’s status individually; all four (SPF, both DKIM CNAMEs, the return-path CNAME) must show verified before MailerSend signs sends from that domain with DKIM.

DMARC is not MailerSend-specific but is required for domains sending more than 5,000 messages per day to Gmail or Yahoo under their 2024 bulk-sender rules. Publish _dmarc.example.com as TXT v=DMARC1; p=none; rua=mailto:[email protected] as a safe starting point; tighten to p=quarantine or p=reject once reports show no legitimate mail failing alignment. MailerSend’s Starter plan includes 30 days of DMARC monitoring inside the dashboard, and Professional keeps it running longer; the bulk sender authentication checklist has the full order of operations.

Once DKIM and SPF verify in the MailerSend dashboard, the DNS auth checker reads how the MailerSend CNAMEs and the apex SPF resolve from a receiver’s perspective, which catches nameserver caches and mistyped selectors before real traffic does.

Generate SMTP credentials

In the MailerSend dashboard, Email > Domains > pick the verified domain > Manage. Scroll to the SMTP section and click Generate new user. The dashboard displays a username and password once, at creation – copy both immediately, because MailerSend does not show the password again after the modal closes. MailerSend’s SMTP credentials are not scoped to a single domain; they authenticate account-wide and can send from any domain the account has verified.

For the API path (WP Mail SMTP Pro’s HTTP mailer option, or a custom integration), the equivalent step is Email > API tokens > Create new token. API tokens can be scoped per-domain with a permission set; the mailer plugins covered on this page all use SMTP, not the API, so SMTP credentials are the default path unless the site has a specific reason to prefer HTTP.

Installing and configuring the official MailerSend plugin

The plugin install is standard: Plugins > Add New > search MailerSend > Install > Activate. Deactivate any other mailer plugin still active on the site before enabling MailerSend’s – two mailer plugins overriding wp_mail() at once is the most common cause of an install appearing to do nothing.

In the MailerSend settings screen, four fields matter. Paste the SMTP username generated earlier into SMTP User. Paste the SMTP password into SMTP Password; the plugin stores the password in the WordPress database, so a hosting environment with database access in a shared context should treat that the same way it treats any other API credential. Set From Email to an address at the domain verified with MailerSend; a From: address at an unverified domain is the single most common first-day rejection. Set From Name to the site or brand name. The WP mail config generator returns the SMTP credential block for the plugin fields.

Save. The plugin does not run a validate-connection check on save; the test-send button below is the confirmation.

Send a test message to an address you can read. The plugin round-trips the send through MailerSend’s SMTP server and reports success or the SMTP error in the admin. A success reply confirms the credentials, sender identity, and outbound port 587 are wired up correctly; verify the message actually arrived at the destination before treating the setup as done, and open the message headers to confirm Authentication-Results shows dkim=pass for ms1._domainkey.<your-domain> and spf=pass for the sending IP. If either fails, the DNS records did not propagate or were entered incorrectly at the DNS host; return to the MailerSend dashboard’s domain page and re-check.

For WP Mail SMTP with Other SMTP, the equivalent settings live under WP Mail SMTP > Settings > Mailer > Other SMTP. Host smtp.mailersend.net, Port 587, Encryption STARTTLS, Authentication PLAIN or LOGIN, Username and Password from the MailerSend dashboard. WP Mail SMTP’s Email Test tab handles the test send. FluentSMTP and Post SMTP use the same field values under their own connection screens.

Sending the first test and reading the failure

The three error patterns worth naming.

535 5.7.8 Authentication credentials invalid. The SMTP username or password was mistyped, was regenerated in the dashboard after the plugin saved, or was pasted with a leading space. Copy the credentials again from the MailerSend dashboard (Domains > Manage > SMTP) and paste them into the plugin. If MailerSend does not show the password (only the username), the credential was generated in a previous session and the password is no longer retrievable; delete that SMTP user and generate a new one.

554 The from header is missing or invalid or a sender-verification failure. The from-address is at a domain MailerSend has not verified, or the DKIM CNAMEs have not propagated. Check the MailerSend dashboard’s domain page shows all records verified for the exact domain in the from-address. [email protected] is a different domain to [email protected] under DKIM alignment rules; verify the domain the site actually sends from, not the domain the site is hosted at.

Connection timeouts or SMTP connect errors. The WordPress host blocks outbound port 587. Some shared hosts block outbound SMTP by default and require a support ticket to open it; some managed WordPress hosts (Kinsta, WP Engine) permit outbound SMTP but log traffic separately. If port 587 is blocked and the host will not open it, the option is switching to a mailer plugin that supports MailerSend’s API over HTTPS – WP Mail SMTP Pro’s Other SMTP mode does not, so the practical alternative is a different provider whose WordPress plugin uses HTTPS (SMTP2GO, Postmark, Amazon SES) rather than SMTP.

The MailerSend Activity feed under Email > Activity shows every send in near-real-time with delivery, opens, and any bounce or complaint reason. Point it at the last hour and the test sends appear near the top; a message that shows Delivered in the Activity feed but has not arrived at the destination is a receiver-side delivery decision, not a MailerSend problem, and the message headers (Authentication-Results, Received-SPF) are where the reason lives.

MailerSend-specific things to know

The MailerSend footer stays on messages until Starter. The free 500-a-month tier and the $7 Hobby tier both stamp a MailerSend footer onto every outgoing message. That footer only removes on Starter ($35/month for 50,000 emails). Sites that are running a real customer touchpoint – order confirmations, receipts, password resets that the site’s brand appears on – should size the plan to at least Starter, or accept the vendor branding as a cost of the free tier.

Log retention is short below Professional. The Activity feed retains one day on Free and Hobby, seven days on Starter, and thirty days on Professional. Sites that need longer retention should either mirror sends to a WordPress email log (Check & Log Email, Log Emails, or WP Mail SMTP’s own log tier) in parallel, or plan for Professional.

MailerSend does not currently publish an EU-region endpoint. All traffic terminates at MailerSend’s US infrastructure. A domain with an EU-resident data policy (a GDPR-focused nonprofit, some public-sector sites) should either accept US processing under the standard contractual clauses MailerSend publishes, or choose a provider that operates EU-region infrastructure (Mailjet, Brevo).

The dedicated IP tier starts at Professional as an add-on, not on Starter. A site on Starter cannot buy a dedicated IP without upgrading. As with any provider, a dedicated IP is worth the money only when the monthly volume clears the roughly 50,000-message threshold below which the IP has too little traffic to build its own reputation.

MailerSend’s free tier caps API requests at 100 per day, separately from the 500-message monthly cap. A site that reads the Activity feed programmatically or checks send status through the API will hit the request cap before the message cap. The plugin path (SMTP without API polling) does not touch the request cap.

When another provider fits better

If the priority is the cheapest free tier that ships without vendor branding, SMTP2GO at 1,000 messages a month with no footer fits better than MailerSend’s 500-with-branding. If the site is on the AWS side of the fence and cost per message dominates the decision, Amazon SES at $0.10 per 1,000 messages is cheaper than MailerSend at every tier. If deliverability at high volume is the priority and the budget supports the price step, Postmark is purpose-built for that. If the site has an EU-resident data requirement, Mailjet‘s EU region fits where MailerSend’s US-only footprint does not. The SMTP cost calculator runs the crossover math against a site’s actual monthly send volume.

Related

When you are ready to go further: