I do a lot of IT work looking after comapnies emails, websites and internet related stuff. One company had all new phones for their staff and on the VodaFone network. For a week after getting them, none could send emails on VodaFone’s network with iphones (worked ok on an office WiFi connection)
A bit of digging and a few phone calls later I found the fix as a alternate SMTP service through VodaFone themselves.
Go to www.360.com have a quick read the click the sign up for free link, making note of your username and password.
On your iphone go to Settings – Mail, Contacts, Calendars then select the account your having sending issues with and scroll down to SMTP
Click into the primary server and enter the below:
host name smtp.360.com
User name the one you created www.360.com
Password the one you createdat www.360.com
Turn Use SSL to ON
Authentication Password
Server Port 645
Using the above settings should stop any issues with VodaFone and sending emails through their service on the iphone.