I just tried to upgrade 5.2.x to 6.0.1 and everything worked well save for our E-mail.
We use a 3rd party server called mDaemon. In 5.2.2 we had just used port mapping for the e-mail to pass through unhindered. As best as i could tell the port mapping remained the same through the upgrade.
Any thoughts on settings under vs. 6?
Thanks,
Matt