Why is Thunderbird connecting to pz-in-f16.1e100.net?
I use Mozilla Thunderbird to access my Gmail accounts. I just set it up and noticed that it was making a continuous connection to pz-in-f16.1e100.net and was downloading something using 99% of my available bandwidth.
A quick lookup revealed pz-in-f16.1e100.net belonged to Google. So was Thunderbird downloading the mails from my Gmail accounts? Yes it was - even though I did not click on the Download / Sync menu.
I think this is a confusing behavior by Thunderbird - it downloads / syncs your mails by default. To prevent that go to the mail accounts setting, under Synchronization and Storage untick "Keep messages for this account on this computer".
The reason I disabled this auto-download feature is because I want to save my bandwidth for other things, and Thunderbird would be downloading mails from three of my Gmail account which have LOTS of mails. Also I don't have the need to have a local copy of the emails, not atleast now.
If you are fine with downloading all your mails from Gmail servers to your computer, you should not have any problems with Thunderbird connecting to pz-in-f16.1e100.net or any servers located at 1e100.net.
One thing I noticed is that the Gmail downloading / syncing servers are located at 1e100.net, for mail 'checking' it is an IP starting with 74.125. Google seems to own all the IPs from 126.96.36.199 - 188.8.131.52.