Ein bißchen Winterstimmung

A user of mine is complaining about not being able to send larger mails (300-500 kB in size) via my exim4 system. It became quite fast obvious that it’s an entropy problem:

# cat /proc/sys/kernel/random/entropy_avail

That’s far too less for Exim4 and SSL/TLS connections.
There’s a (closed) bug in the BTS, but there’s no real solution mentioned. As the bug is closed with comment like “seems to be vanished somehow”, but it’s happening still on my Etch server I’m somewhat unsure what to do now?

Building Exim4 with openssl support instead of gnutls? That would be a maintenance nightmare.
Ignoring the problem and don’t care? That wouldn’t make my users happy.
Switching to another MTA like postfix? That wouid mean lot of work, because everything would need to be changed on my system.

Is there any simple solution for the Exim4 entropy problem available, dear lazyweb?