I'm running outlook 2013 on 5 computers in a small office, using POP3 for everyone's personal accounts, and I've recently set up an IMAP account so that we can have a single email address whose emails are accessible by all of us. Since setting these up we've noticed a huge jump in bandwidth usage from our host which is all in IMAP traffic.
I've just checked and it seems that whenever I hit send/receive in Outlook, my "Received" data count in my Network Settings> Ethernet Status jumps up by approx 10mb even when there are no new messages. The IMAP account we've set up is new and there are only about 20 emails, some of which have attachments, totalling maybe 10-15mb. As I understand it, when I Send/Receive mail it should only be downloading new messages - is there a possibility that it's actually downloading the full content of the IMAP inbox each time? If so what can I do to change this?
I'm having the same issue on at least two computers in the office - both are running outlook 2013 on Windows 10 and appear to be set up the same in terms of the account settings. I've tried googling and couldn't turn up anything relevant.