Question regarding Apple Mail and my internet connection dying...

Hey guys i have a very weird problem here. At work we have Bell Optimax 8mb/s down 1mb/s up.
My boss has apple mail and i have configured it with 12 email accounts all connected via GMAIL IMAP (Google apps professional). Now when the mail app is open, the internet crawls to a stand still, we are talking about 1000ms pings, 0.5mb/s download speeds in speed test. When i close the mail app all of a sudden everything is perfect.

This is a very weird issue and i have never seen this before... Can 12 mail accounts bring down a whole connection on its own? Nobody else is actually on the network when i do this...

And also the usage on these email accounts is about 20-30 emails in a day...

Does anyone have an idea what this program is doing?

Also when i check activity stats on apple mail for the 1 account it hasnt recieved anything since april 15 and under usage it is saying its

Traversing mail box hierarchy
Adding messeges
Checking status of mail box

These things just keep running all day every day. That specific account has just a spinning icon on it constantlly.

Any ideas guys?

Thanks a lot,

Dani