Title: SMTP Add-on issues?
Last modified: May 29, 2026

---

# SMTP Add-on issues?

 *  [GeoffBel](https://wordpress.org/support/users/geoffbel/)
 * (@geoffbel)
 * [1 week, 2 days ago](https://wordpress.org/support/topic/smtp-add-on-issues/)
 * Great plugin overall!
   I am trying to improve the delivery of the Newsletter plugin,
   but I am hitting a wall.For context, my client has been using the default WP 
   mailer with this plugin for a while.Unfortunately, several mail services are 
   now rejecting emails sent in that way as they do not look super legit for spam
   filters. Long story short, many emails are no longer reaching destination.My 
   initial instinct was simply install something like WP Mail SMTP on the site, 
   but for some reason that is not compatible with your plugin for some reason. (
   Email Source: Newsletter Mailer: Other SMTP SMTP Error: data not accepted. SMTP
   server error: DATA END command failed Detail: Non-Compliant sender address. Code:-
   2 SMTP code: 550 Additional SMTP info: 5.7.1)So I turned to your proprietary 
   SMTP add-on, but still no joy. No matter what combination of protocol (SMTP+STARTTLS
   or SMTPS) and port I try with the add-on it always fails (SMTP Error: data not
   accepted. SMTP server error: DATA END command failed Detail: Non-Compliant sender
   address. Code : -2 SMTP code: 550 Additional SMTP info: 5.7.1)
 * For the record, when entering the exact same combination of port, authentication
   details and protocol with WP Mail SMTP, the emails are sent without any problems.
   
   Any suggestion other than switching to an email sending service (MailGun, etc..)?
 * By the way, I am surprised that there is no SSL option in this add-on. Just SMTPS?
 * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fsmtp-add-on-issues%2F%3Foutput_format%3Dmd&locale=en_US)
   to see the link]_

Viewing 1 replies (of 1 total)

 *  Plugin Support [Michael Travan](https://wordpress.org/support/users/michael-travan/)
 * (@michael-travan)
 * [1 week, 2 days ago](https://wordpress.org/support/topic/smtp-add-on-issues/#post-18923606)
 * Hello,
 * I think there are some misconceptions going on here but no worries, we’re here
   to help! The message you’re receiving both with Wp Mail Smtp (which we highly
   suggest) and with our own smtp addon (which we don’t suggest using and will be
   discontinued, eventually) tells the same story: the sender address is non-compliant,
   that means your domain is failing to comply with one or more security protocols.
   First of all: is the sender address domain the same as your domain? How about
   Spf, Dkim, and Dmarc records? Are those correctly in place? The first thing I
   would do is to check your sender address with a tool like mail-tester.com and
   see what indications it gives you.
 * Michael

Viewing 1 replies (of 1 total)

You must be [logged in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fsmtp-add-on-issues%2F%3Foutput_format%3Dmd&locale=en_US)
to reply to this topic.

 * ![](https://ps.w.org/newsletter/assets/icon-256x256.png?rev=1052028)
 * [Newsletter - Send awesome emails from WordPress](https://wordpress.org/plugins/newsletter/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/newsletter/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/newsletter/)
 * [Active Topics](https://wordpress.org/support/plugin/newsletter/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/newsletter/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/newsletter/reviews/)

 * 1 reply
 * 2 participants
 * Last reply from: [Michael Travan](https://wordpress.org/support/users/michael-travan/)
 * Last activity: [1 week, 2 days ago](https://wordpress.org/support/topic/smtp-add-on-issues/#post-18923606)
 * Status: not resolved