Postfix: 550 No Such Domain at this Location

Question

I am trying to configure Postfix on a Linux server to only send outbound mail. I have followed the null client tutorial and my Postfix settings are set according to that tutorial.

The email is never sent. I am trying to send to a gmail address. The relay shows mail.mydomain.com followed by my mail MX record. The gmail account is valid.

Can someone please tell me what may need to change in my configuration. If more details are needed, let me know.

The error message I am concerned with:
postfix/smtp[16925]: 2536E5B8A: to=<[email protected]>, relay=mail.domain.com[xx.xx.xx.xx]:25, delay=0.32, delays=0.04/0.01/0.12/0.15, dsn=5.0.=5.0.0, status=bounced (host mail.domain.com[xx.xx.xx.xx] said: 550 No such domain at this location (in reply to RCPT TO command))


All of the error messages for completeness:
postfix/pickup[16383]: 2536E5B8A: uid=33 from=<www-data>
postfix/cleanup[16923]: 2536E5B8A: message-id=<20130321235015.2536E5B8A@removed>
postfix/qmgr[16384]: 2536E5B8A: from=<[email protected]>, size=426, nrcpt=1 (queue active)
postfix/smtp[16925]: 2536E5B8A: to=<[email protected]>, relay=mail.domain.com[xx.xx.xx.xx]:25, delay=0.32, delays=0.04/0.01/0.12/0.15, dsn=5.0.=5.0.0, status=bounced (host mail.domain.com[xx.xx.xx.xx] said: 550 No such domain at this location (in reply to RCPT TO command))
postfix/cleanup[16923]: 7763F5B8C: message-id=<20130321235015.7763F5B8C@removed>
postfix/qmgr[16384]: 7763F5B8C: from=<>, size=2505, nrcpt=1 (queue active)
postfix/bounce[16926]: 2536E5B8A: sender non-delivery notification: 7763F5B8C
postfix/qmgr[16384]: 2536E5B8A: removed
postfix/smtp[16925]: 7763F5B8C: to=<[email protected]>, relay=mail.domain.com[xx.xx.xx.xx]:25, delay=0.26, delays=0.01/0/0.09/0.16, dsn=5.0.0, status=bounced (host mail.domain.com[xx.xx.xx.xx] said: 550 No such user ([email protected]) (in reply to RCPT TO command))
postfix/qmgr[16384]: 7763F5B8C: removed

Solution

It seems that:
Postfix at your host tries to use mail.domain.com as smart/relay host
mail.domain.com refuses to relay

It may mean that:
You configured wrong smart/relay host OR
The host requires SMTP AUTH to relay

Comments

[Jenny D]

OR - they forgot to add their own ip address to the list of clients allowed to relay mail via that server.