Im not too sure that its completely with gmail- if it is I would like to investgate if SME Email service (qmail) is able to compensate by extending the timeout limit. I find that the the problems occur when either the attachments are large or when transfering emails to gmail or other third party web/email servers.
e.g When transfering the email to gmail, i may get through a quarter of the emails (2880) and then disconnests. I am using gmails pop connector to import the emails when the issues occur. The total data to be downloded for the emails is appx 700MB. Obviously when the process is repeated there are multiple copies of a particular email...
I have the same issues when using SBS 2003 pop connector to pull the emails off the SME 7.52 server.