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✉️ Email Delivery

Documentation, reference material and tutorials for CRM-NG SMTP Email: setup guides for every mail service, troubleshooting, and one article per error message.

Error: 553 Sender address rejected: invalid sender email address

Updated

By Duane GarnerChief Executive Officer (CEO)
Summarize: Claude ChatGPT View Markdown
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The SMTP server will not send from your From address. Use the mailbox you log in with, or an alias it is allowed to use, and force it.

Shown by SMTP-based sending (Other SMTP, Zoho Mail, the backup SMTP transport)

The test result or the error log shows a reply starting with 553, for example 553 Sender address rejected: not owned by user or 553 5.7.1 Sender address rejected.

This article is for site owners sending through an SMTP server whose From address is refused.

What this error means

Reply code 553 means the server refused an address in the message as not allowed. With "sender address rejected", the problem is the From address (the envelope sender). Most mail servers only let a logged-in account send as its own address and any aliases set up for it. If the message claims to come from someone else, the server stops it to prevent forgery.

It is permanent: the same message from the same address will be refused again.

Common causes

  • From Email is different from the mailbox in SMTP Username, and that mailbox has no permission to send as it.
  • Zoho Mail: the From address is not the Mailbox Email Address or one of its configured aliases.
  • Another plugin, such as a form or shop plugin, sets its own From address (often the visitor's address), and Force From Email is off.
  • From Email is empty, malformed or uses a domain the server does not handle, such as wordpress@localhost.
  • Return Path is on and the server does not accept the resulting sender.

How to fix

  1. Check which addresses the mailbox may use

    In your mail provider's admin console, look at the mailbox's addresses and aliases, or "send as" permissions. In Zoho Mail, aliases are listed in the mailbox's settings.

  2. Set the From address

    Go to CRM-NG SMTP → Settings → General and set From Email to the login mailbox or an allowed alias.

  3. Force it

    Turn on Force From Email so other plugins cannot replace it. Visitors' addresses belong in Reply-To, which most form plugins can set.

  4. Check Return Path

    If the error continues, try turning Return Path off and test again.

  5. Save and test

    Save the settings, then go to CRM-NG SMTP → Tools → Email Test, fill in Send To and press Send Email.

Verify it worked

The test page shows "Test email sent successfully! Check your inbox to confirm delivery." The received message shows your chosen From address.

Notes

  • To send from several addresses, add them as aliases on the mailbox at your provider first, then turn Force From Email off and let each plugin use its alias.
  • For Microsoft 365 the equivalent problem appears as ErrorSendAsDenied; see that article.
  • Using a form visitor's address as From also fails SPF and DMARC at the recipient. Keep your own domain in From.
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