downloading e-mail is blocking network

[Chuck Swiger]

Hi, Marco--

On May 19, 2010, at 12:15 PM, Marco Beishuizen wrote:
> I'm having a strange network problem. Every day, when I turn on my computer, fetchmail is started and procmail is putting all my mail in the correct mailboxes. This takes some time because I receive a few hundred e-mails a day (mostly mailing lists).
> 
> The strange thing is that when the e-mail is being downloaded, all other network traffic seems blocked. So browsing the internet is not possible when fetchmail/procmail is busy. At first I thought I had a problem with DNS and/or DHCP and/or my ADSL modem because after a reset of the modem, the problem mostly went away, and there were some "hostname not found" errors in my logfiles. But today I just waited for a while and discovered that when fetchmail/procmail is finished, the internet suddenly was reachable again.
> 
> So has anyone has seen fetchmail/procmail blocking network traffic before?

Are you using NAT?

It sounds like something has a limited number of NAT state slots available, and is dropping connections past that limit.  It probably will help to try to serialize the activity of fetchmail / procmail so that they aren't opening new connections for every email being processed, if that is what is going on.

Regards,
-- 
-Chuck