DSN Service Unavailable

centos smtp sendmail

8,278

It might have mx record setup issue. Run the following command:

dig site.com mx

where site.com is your domain name.

In the output you will see Question section it is question to find the MX. In answer section you will find the mx entries configured for the domain. Check the mx records if they are correct.

Sample output is given below: where there 3 mx record entries like ASPMX.L.GOOGLE.com., ALT1.ASPMX.L.GOOGLE.com. etc

;; QUESTION SECTION: ;thestarworks.com. IN MX

;; ANSWER SECTION: thestarworks.com. 3600 IN MX 10 ASPMX.L.GOOGLE.com.
thestarworks.com. 3600 IN MX 20 ALT1.ASPMX.L.GOOGLE.com.
thestarworks.com. 3600 IN MX 30 ALT2.ASPMX.L.GOOGLE.com.

8,278

Lock

Updated on September 18, 2022

Comments

Lock almost 2 years
I am having trouble with a newly installed server that we have just migrated to. I am running sendmail and cannot send mail to a specific domain. Mail everywhere else appears to work. Logs say:
```
DSN: Service unavailable
```
Weirdly, I get a Message accepted for delivery and then a following entry to say DSN: Service Unavailable.

Why would this be? I do not have it relaying through a smart host. The server that I am sending from does not have a public IP and is purely for sending mail from a PHP application.

Any advice appreciated as Google hasn't been a big help.
- Bernardo Augusto almost 12 years
  
  Do you have something else in your logs?
- adaptr almost 12 years
  
  I suspect you don't actually know what DSN means. Sendmail is telling you that it tried to send the message using the ESMTP extended syntax, but the remote server didn't like that.
- cjc almost 12 years
  
  One possibility: the remote server thinks you're spamming, or is greylisting you.
- John Gardeniers almost 12 years
  
  Are you sure you don't mean DNS? A DSN is something used to connect to databases. It's not a service.
- dunxd almost 12 years
  
  DSN can also stand for Delviery Status Notification (RFC 3461 - tools.ietf.org/html/rfc3461)
- Lock almost 12 years
  
  Thanks for the comments. I know what DSN stands for (not to be confused with DNS). I believe it is the server rejecting the email, as the log takes a few seconds before it shows that it failed. Is there anywhere else I can take a peek that shows a more detailed message?
- Lock almost 12 years
  
  Update: found in /var/spool/mail/root the following: (reason: 552 sorry, your envelope sender domain must exist (#5.7.1))