Postalion

Documentation

Sending and SMTP

Postalion does not run a mail service of its own. It hands every email to your site, and your site hands it to a mail server. This page is about that second step, because it decides whether your newsletters arrive.

Two ways out

WordPress mail is the default: the wp_mail() function, as set up by your host or by a mail plugin you already use (WP Mail SMTP, FluentSMTP, Post SMTP and the like). When such a plugin is active, Postalion notices and leaves it in charge.

SMTP server means Postalion talks to a mail server itself: your own, your host's, or a sending service. Pick it under Settings → Sending method and fill in:

  • Server and port: as given by the service, for example smtp-relay.brevo.com and 587.
  • Security: STARTTLS on port 587 for almost every service, SSL/TLS on 465, none on 25 for a local server.
  • Login: username and password, or no login for a server that trusts your site's address.

Press Send test before you save: it uses the values as they are in the form, and shows the server's answer when something is wrong ("could not authenticate", "connection refused"), so you can fix it on the spot.

The password is stored encrypted with the security keys of your site. If you would rather keep it out of the database, define it in wp-config.php:

define( 'POSTALION_SMTP_PASSWORD', 'your-password' );

A switch below the fields, Use this server for all the mail of this site, routes password resets, order emails and contact forms through the same server. Turn it on when the site has no other mail plugin.

Which service?

Any SMTP service works. Brevo, Amazon SES, Mailgun, Postmark and SendGrid are common choices, each with a free or cheap tier that covers a small newsletter. Your hosting company's mail server works too, but shared servers are often blocklisted, which is the usual reason newsletters vanish.

Whatever you pick, two things apply: the sender address in Settings must be one the service has verified, and your domain needs SPF, DKIM and DMARC records that mention the service. The service shows you the records to add; without them Gmail and Outlook file bulk mail as spam or refuse it.

Batches, pauses and WP-Cron

A newsletter is never sent in one request. Postalion puts every recipient in a queue, sends the first batch at once and the rest through WP-Cron, with a pause between batches. The defaults, 10 emails every 5 seconds, suit shared hosting; Settings → Sending speed lets you go up to 50 per batch and pause up to an hour, so the send stays inside your service's limits.

WP-Cron runs when someone visits the site. On a quiet site a real cron job that calls wp-cron.php every few minutes makes scheduled sends punctual; the dashboard's System card tells you whether cron is on. An interrupted send resumes where it stopped, and nobody gets the same email twice.

When emails do not arrive

  1. Check the Logs screen: a failed email shows the reason the server gave.
  2. Look in the spam folder of the test address.
  3. Make sure the sender address is on your domain and verified with the service.
  4. Check the SPF, DKIM and DMARC records at your DNS provider.
  5. Send a test from Settings → Sending method with the values typed in again.

Next: Sign-up forms