email constantly full

It's obvious that Xfinity lowered the size of their email storage a few months--it's a nightmare for me because I get lots of emails and they forward to Outlook, but I get it.
  I had gotten in the habit of going in once a day and deleting ALL the emails (because they had already forwarded to Outlook), and then going in emptying the trash, spam etc, so that there are NO emails remaining.

  My problem is that this morning, when there were only 30 emails (all smaller size and only one with an attachment) it was already saying my email was 98% full--these emails surely did not add up to the 10GB limit.   I've been on the phone with Xfinity all morning; their only solution is to delete more email.  I really don't have time to go in every couple of hours to delete emails that actually haven't hit my size limit.   I'm ready to switch to a different company and this has become a major time-waster, and I think the size limit is ridiculously small for anyone that gets a normal amount of email a day?  Any suggestions?