Title: SMTP server error 5.1.1 User unknown
Last modified: August 20, 2016

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# SMTP server error 5.1.1 User unknown

 *  Resolved [rsanchez1123](https://wordpress.org/support/users/rsanchez1123/)
 * (@rsanchez1123)
 * [13 years, 5 months ago](https://wordpress.org/support/topic/smtp-server-error-511-user-unknown/)
 * I’m having an odd problem with email that I could use some help debugging.
 * I have a dev server and a live server for my wordpress site. The problem I’m 
   having is that I’m trying to email a particular email address. The email gets
   sent just fine from my dev server, but it fails sending from my live server. 
   My dev and live servers are on different domains, and the email address I’m trying
   to send has the same domain as my live server.
 * On both servers, I have it set to use SMTP, and on the live server it is giving
   me this error:
 * SMTP server error: 5.1.1 … User unknown
 * The only SMTP options I have set from the Advance Email Options page are:
 * SMTP Host: localhost
    SMTP Port: 25 Encryption: No encryption.
 * This definitely has me stumped. The live and dev servers are pretty much identical,
   except for the domain name. I think the domain name might be an issue, but I’m
   not sure. I’d appreciate any help with this.

Viewing 1 replies (of 1 total)

 *  Thread Starter [rsanchez1123](https://wordpress.org/support/users/rsanchez1123/)
 * (@rsanchez1123)
 * [13 years, 5 months ago](https://wordpress.org/support/topic/smtp-server-error-511-user-unknown/#post-3242322)
 * Ok, I found what the problem is after a little more googling. This page helped
   resolve it for me:
 * [http://serverfault.com/questions/65365/disable-local-delivery-in-sendmail/128450#128450](http://serverfault.com/questions/65365/disable-local-delivery-in-sendmail/128450#128450)

Viewing 1 replies (of 1 total)

The topic ‘SMTP server error 5.1.1 User unknown’ is closed to new replies.

## Tags

 * [email](https://wordpress.org/support/topic-tag/email/)

 * In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/)
 * 1 reply
 * 1 participant
 * Last reply from: [rsanchez1123](https://wordpress.org/support/users/rsanchez1123/)
 * Last activity: [13 years, 5 months ago](https://wordpress.org/support/topic/smtp-server-error-511-user-unknown/#post-3242322)
 * Status: resolved

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