[Mailman-Users] Mailman working, but very slow delivery of posted mails

[Mal]

Hello, I am running mailman / postfix on Ubuntu 6.06 (using apt-get
latest standard versions)

I have everything working correctly, except that when people send
mails to the list, it takes on average one hour to send the mails out
to subscribers!!

The volume is only small now, as we are testing with only three people..

I have searched this list, but can not find an answer for slow
delivery times on systems where mail volume is very low.

If you have a clue what I could be missing, I would LOVE to get your advice.

Thank you
Mal