Ubuntu – Postfix refusing to relay mail from local client

postfixpythonsmtpUbuntu

I'm trying to get a python script to send mail (using smtplib.SMTP), but postfix is refusing to relay the message. I don't use the Ubuntu 10.10 Virtualmin server as a mail server (I happen to use google apps for that), but I want scripts to be able to send mail. Here is the log, with the addresses replsced with generic ones:

Apr 11 00:50:27 unimatrix-01 postfix/smtpd[25212]: connect from localhost[127.0.0.1]
Apr 11 00:50:27 unimatrix-01 postfix/smtpd[25212]: NOQUEUE: reject: RCPT from localhost[127.0.0.1]: 554 5.7.1 <example@gmail.com>: Relay access denied; from=<noreply@example.info> to=<user@gmail.com> proto=ESMTP helo=<unimatrix-01.example.com>
Apr 11 00:50:27 unimatrix-01 postfix/smtpd[25212]: lost connection after RSET from localhost[127.0.0.1]
Apr 11 00:50:27 unimatrix-01 postfix/smtpd[25212]: disconnect from localhost[127.0.0.1]

I have already tried with no success, to fix this by running # dpkg-reconfigure postfix according to the Ubuntu Docs. How can I fix this?

Thanks in advance.

Update: Interestingly, apps using PHP can send mail just fine. So, I suspect it has something to do with postfix requireing authentication locally. This is not necessary as I am use sole user of this VP. I hope this helps with troubleshooting.

Best Answer

Check if you permit local networks to relay emails without authentication.

First of all, the following command, should include permit_mynetworks

sudo postconf smtpd_recipient_restrictions

Then check if 127.0.0.1 is in $mynetworks. Just do,

sudo postconf mynetworks

and check if 127.0.0.1 is there.

Related Solutions

Linux – How to correct Postfix’ ‘Relay Access Denied’

TLS just enables encryption on the smtp session and doesn't directly affect whether or not Postfix will be allowed to relay a message.

The relaying denied message occurs because the smtpd_recipient_restrictions rules was not matched. One of those conditions must be fulfilled to allow the message to go through:

smtpd_recipient_restrictions =
    permit_sasl_authenticated
    check_recipient_access hash:/etc/postfix/filtered_domains
    permit_mynetworks
    reject_unauth_destination

To explain those rules:

permit_sasl_authenticated

permits authenticated senders through SASL. This will be necessary to authenticate users outside of your network which are normally blocked.

check_recipient_access

This will cause postfix to look in /etc/postfix/filtered_domains for rules based on the recipient address. (Judging by the file name on the file name, it is probably just blocking specific domains... Check to see if gmail.com is listed in there?)

permit_mynetworks

This will permit hosts by IP address that match IP ranges specified in $mynetworks. In the main.cf you posted, $mynetworks was set to 127.0.0.1, so it will only relay emails generated by the server itself.

Based on that configuration, your mail client will need to use SMTP Authentication before being allowed to relay messages. I'm not sure what database SASL is using. That is specified in /usr/lib/sasl2/smtpd.conf Presumably it also uses the same database as your virtual mailboxes, so you should be able enable SMTP authentication in your mail client and be all set.

Relay access denied and policy rejection errors

The first error message is just what it says, an attempt to relay mail through your system was rejected. Another ServerFault question touches on this, and may be of use:

How to correct Postfix' 'Relay Access Denied'?

Related Topic