The remote host is missing an update to fetchmail announced via advisory USN-816-1.
Details follow:
Moxie Marlinspike discovered that fetchmail did not properly handle certificates with NULL characters in the certificate name. A remote attacker could exploit this to perform a man in the middle attack to view sensitive information or alter encrypted communications.
Solution: The problem can be corrected by upgrading your system to the following package versions:
Ubuntu 6.06 LTS: fetchmail 6.3.2-2ubuntu2.3
Ubuntu 8.04 LTS: fetchmail 6.3.8-10ubuntu1.1
Ubuntu 8.10: fetchmail 6.3.8-11ubuntu3.1
Ubuntu 9.04: fetchmail 6.3.9~ rc2-4ubuntu1.1
In general, a standard system upgrade is sufficient to effect the necessary changes.