Postfix – Phocean.net

Postfix : TLS not working outside my network

phocean — Tue, 10 Jun 2008 23:37:28 +0000

As I just finished setting TLS and SASL to secure the access to my Postfix server, I realized that it was working only from inside my network.

What I got from my lan :

$ telnet mars 25
Trying 192.168.222.10...
Connected to phocean.net.
Connected to phocean.net.
Escape character is '^]'.
220 phocean.net ESMTP Postfix (Debian/GNU)
220 phocean.net ESMTP Postfix (Debian/GNU)
ehlo phocean.net
ehlo phocean.net
250-phocean.net
250-phocean.net
250-PIPELINING
250-SIZE 200000000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH NTLM DIGEST-MD5 CRAM-MD5
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

I shows well that the TLS handshake is initiated.

But from this outside, I just got this weired thing :

$ telnet phocean.net 25

$ telnet phocean.net 25
Trying 81.64.194.119...
Connected to phocean.net.
Connected to phocean.net.
Escape character is '^]'.
220 **********************************************
ehlo phocean.net
ehlo phocean.net
502 5.5.2 Error: command not recognized

Of course, the firewall, a Cisco Pix one, was properly set to redirect port 25 UDP/TCP to my server.

However, I soon focused my effort on this equipment. I considered a while that the cause could be some filtering from my provider, but most probably, the problem came from the Pix.

That was not difficult to figure out : it had some protocol inspector activated for SMTP :

$ sh ru
[...]
fixup protocol smtp 25
[...]

Just after :

> no fixup protocol smtp 25

… it started to work perfectly well !!!

The engine for the SMTP protocol could not recognize the TLS handshake, considered that the SMTP session as not valid and therefore blocked it !

I can deactivate it without any fear as my Postfix server is already pretty well secured, or at least configured to reject any weired SMTP dialog.

Postfix : “error writing message: File too large”

phocean — Sun, 01 Jun 2008 21:13:49 +0000

I suddenly started to received some undelivered mail notifications while I was trying to send some messages to a mailbox hosted on my Postfix server.

The cause described in the notification was :

error writing message: File too large

The first thing I did was checking my configuration file, main.cf.
It seemed all right :

[...]
mailbox_size_limit = 0
message_size_limit = 200000000
[...]

Note that “0” means unlimited.
I checked the mailbox in question : it was nearing the size of 50 Mb.

I started to think that during some Postfix update, the meaning of the value “0” may have changed.
I tried different values without success.

I started to become crazy with that, but, finally, after quite a long time spent on google, I finally found the trick, which is just a simple line to add in main.cf :

virtual_mailbox_limit = 0

Indeed, I use virtual users as mail account ! I just never imagined there was a differtent setting for virtual users (which can be a convenient setting in some case).

Hostname issue with Postfix Webmin module

phocean — Fri, 12 Jan 2007 18:38:00 +0000

I usually avoid using Webmin, but I had to set it up for a company I worked for.

The guys there were not familiar with Linux and they needed an interface to keep configuring the Postfix server I settled (with Spamassassin as an antispam and Amavis as content filtering).

I had to face a problem while I was trying to get the Postfix Webmin module working.

The error message was quite cryptic. Just this single line on a blank screen every time I tried to apply a configuration change :
usr/sbin/postconf: fatal: gethostbyname: Success

After looking on the net, I learned that this Webmin module uses the getbyhostname() function to resolve the server name, instead of using the DNS service as Postfix do.

Therefore, the message indicates that the machine name could not be resolved for some reason.
There are several possibilities.

First, check your /etc/hosts file, it must contain your machine name

Then, in your /etc/postfix/main.cf configuration file, you might have this line (especially on Debian systems) :

myorigin = /etc/mailname

If so, check that /etc/mailname contains your machine name, as /etc/hosts do.

Finally, also check that in /etc/postfix/main.cf, the myhostname field is correct :

myhostname = mail.phocean.net

myhostname = mail.phocean.net

If you made any change in main.cf, restart postfix and that should be fine !