Read this thread:
Z10 encoding issue in outgoing email - Page 5 - BlackBerry Support Community Forums
And especially this:
http://supportforums.blackberry.com/...2231991#M10389
The problem lies with the Z10's software.
Changing provider for an entire site because a small batch of new smart phones cannot connect (due to an OS problem with the new cell phones) is never going to happen. I say it's not a solution, because it's such as BAD solution, that it will not get approval. Changing the phones is quick and easy, changing (and punishing our existing) provider because BlackBerry have a problem with the software "mangling message headers" is bad on multiple levels.
We aren't losing time or money (but thank you for your concern) on this at the moment, however we ARE running out of patience. If BlackBerry don't update the software and make it work with these IMAP accounts (not only Zenutech is affected), then it will be impossible for us to defend keeping our new phones. I'm surprised it is taking this long to fix such a core component of the phone's OS. It's been out since February and it's nearly May now.