[RndTbl] strange IMAP / G3 problem

[Trevor Cordes]

Brad & I are having a weird problem with his iphone 4S (with the latest 
iOS versions).

iphone builtin mail
imaps (port 993)
ssl (self-signed) (old ciphers disabled on server)
dovecot

He can connect to imap with the above config on his in-office wifi, 
in-home wifi over vpn to office, and shaw open wifi outside his 
office/home network.

If he switches to 3G (I don't think his phone does LTE) then suddenly he 
can't connect!  (With some useless "can't connect" error.)

Huh?  Duh?

Exact same setup and settings on an iphone 5 works fine.  Also works fine 
on Android.  The problem is just on his 4S.

Even more interesting, if he wifi tethers a PC to his 4S over 3G and hits 
imaps using thunderbird on the PC it works fine.

My question is, what on earth does changing the connection layer have 
anything to do with this?  Can the phone be doing something differently in 
the mail app depending on 3G or wifi???  Can the 3G network be blocking 
something (unlikely since the tethered PC works)?  It make no sense 
whatsoever to me.  Maybe his phone is p0wned?  I'm stumped.  Ideas?