IPhone email not working on 3G/4G

Question

Hi Everyone
I’m having a problem with accessing email on the IPhones over the 3G/4G network
The email addresses are setup for IMAP and are put on a mixture of mobile phones however quite  a large amount of them are on the IPhone 4s/5. The IPhones could access the emails without any problems through both wifi and 3G/4G until a few days ago when the 3G stopped working.
I checked a few things on the email accounts which was ok, Firstly I deleted the email addresses and re added them to IPhone and restarted, no luck, the users who have the IPhones have upgraded to IOS7 but this issue seemed to start before they upgraded, I spoke to EE (the mobile provider) who advised me to speak to Apple who advised to do a network settings reset which did not work and  then they advised doing a full factory reset, which I have not tried yet but that does seem extreme  to access emails over the 3G connection working
Other phones synch/access the email fine over 3G/4G such as htc’s, samsungs and sony ericssons, and Blackberrys so the server and the settings are ok, we are just having  this problem with the Iphone’s
Any help is very much appreciated
Thanks

Answer 1

I had a similar problem with emails not sending on 3G, which must have started at about the same time, although it took a while to notice as emails were swooshing on send and not reporting any failure. But they weren't getting to people and on closer inspection they weren't going into sent folders. I'm on EE too, with an iPhone 4.
Anyhow, I found someone saying they had solved a similar problem by ejecting and reinserting the sim, and that's just worked for me.