I am using a mutt setup with msmtp (msmtp-enqueue script) and fetchmail to send and reeive mails.

For Internet I use a mobile phone with GPRS Internet connection and IrDA connection to the zaurus.

Now, when I try to send and receive mails via the mobile phone, msmtp-runqueue sends one mail and then the GPRS connection is gone suddenly, causing msmtp to report a DNS failure. This happens always exactly after sending one mail.
Fetching mails with fetchmail eems to work well, even if there are more than ten messages waiting on the server.

Does anyone have an idea where to look for the reason of the problem?
Could it be an IrDA timeout? But why does it occur with msmtp but not with fetchmail?

Where can I try to tweak, e.g. in /proc/sys/net/irda/* ?

Thanks a lot!