I have two different POP3 accounts under two different domains. I was using my Samgung Galaxy S2 (I9100 unrooted, unlocked) with stock Gingerbread (2.3.6) and my monthly data usages for emails were ~100 MiB. But, after upgrading stock ICS (4.0.3 I9100XWLP7-Turkiye), in a single day it was ~50 MiB. Due to this reason I've switched K9 client. But, it constantly deleted all of my account settings in a random interval. After realizing it's a known bug for a long time, I've desperately returned stock email. After several tries, a friend of mine advice to "mark all messages as read" immediately after setting accounts to prevent excessive traffic usages. At first, this doesn't make sense to me, but he explained that some old Windows-based email clients were acting in that way (unread messages were constantly downloaded over and over again). Interestingly, it worked. But, after using it for a while (precisely 1-2 days), "Onavo Count" started to warn me again about that email client consumes too much traffic. While investigating the problem, I've noticed that for a single check, it consumes 1-3 MiB traffic even though I've marked all messages as read. And now email client reached ~300 MiB traffic usages in total (I've only 1 GiB/month data plan).
As a summary:
- I was happy with Gingerbread email client.
- ICS client consumes too much traffic for each check.
- K9 was tried. It's very buggy.
- I don't want to add my POP3 accounts to Gmail to avoid excessive traffic usages (using push notification and such).
- I don't want to pay an app due to such thing (why should I use Android if even I can't read my emails properly!?). I was happy with stock client. If there is way that I could use it, I prefer that way.
- I don't want to root my device due to such problems
- As a last attempt, I could even write my own client which could optimize traffic usages (check only header on 3G connection, download all emails on WiFi etc.)
EDIT: Seems something is not right with Onavo Count. It frequently warns me about email client (now ~650 MiB) even though I've increased check interval "5 min" to "once a day". And what's more, Onavo Count reports my total traffic usage as ~6 GiB now (still increasing). But, according to ICS's built-in data monitor and my operator I didn't used that much traffic (only ~1 GiB). But again, this doesn't changed the fact that email client consumes too much data (around ~200 MiB which means x2 after upgrading to ICS, it's verified by both ICS's built-in data monitor and my operator reports).