Can't send mail ISPconfig 3

  • Posted September 13, 2014

Hello again!

I’ve a problem with sending mails by squirrelmail (ispconfig3 server).

I can recieve mails but i cannot send and no idea where is the error.

The configuration is the following:

1 domain added to DNS panel and with digitalocean nameservers, same domain added on ISPconfig as domain, mailbox, etc…

Thanks for reading.


That almost looks like outbound port 25 is being blocked.

Try telnet 25

You should see a response back

Connected to
Escape character is '^]'.
220 ESMTP qi10si18484053pbb.216 - gsmtp

Type “quit” to exit.

Hi there; I was in touch with support about this a few months back and I didn’t realise it was still blocked.

The response was:

… the changes you need to make are in /etc/gai.conf

Look for the list of precedences that are commented out.

The last value simply needs to be uncommented and the 10 changed to a 100

This will de-prioritize IPv6 NS lookups and allow IPv4 to take priority.

Eventually we will remove the block on IPv6 SMTP, but for now it will remain in place.

Or, to put it another way:


nano /etc/gai.conf

make the appropriate lines look like this

precedence ::ffff:0:0/96  100

Reboot, test, enjoy, let me know if it works :)

I can send emails to myself and i recive it.

-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- BB4094147E* 1432 Sat Sep 13 19:03:35

40FBF41434 1389 Sat Sep 13 03:05:57 (connect to[]:25: Connection timed out)

658DE41478 1428 Sat Sep 13 17:57:36 (connect to[2404:6800:4008:c00::1a]:25: Network is unreachable)

6802D41460 1423 Sat Sep 13 19:03:51 (connect to[2404:6800:4008:c00::1a]:25: Network is unreachable)

6F3D641143 2165 Fri Sep 12 19:35:22 (connect to[2404:6800:4008:c01::1a]:25: Network is unreachable)

DDF5B413F1 1405 Sat Sep 13 16:50:57 (connect to[2404:6800:4008:c00::1a]:25: Network is unreachable)

1B8404142A 1182 Sat Sep 13 03:03:27 (connect to[2404:6800:4008:c00::1b]:25: Network is unreachable)

C3618413F7 1403 Sat Sep 13 17:40:01 (connect to[2404:6800:4008:c00::1b]:25: Network is unreachable)

Submit an answer
You can type!ref in this text area to quickly search our full set of tutorials, documentation & marketplace offerings and insert the link!

These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.

Hi again vps and thanks for your time, i did telnet to that server thow port 25 as you told me and i think the problem is there:

Trying (my ip)… Conected to mydomail.tld Escape character os ‘]^’. 220 server.mydomain.tld ESMPT postfix (Debian/GNU).