GMail problems sorted
I had this problem too, but I think I have sorted it now. I have 2 Gmail accounts and both were working previously. With my new 4S, one would crash on send every time and the other would not.
Contacted support who were very polite but did not have a solution. After lots of playing I worked out this solution.
1. Delete all email accounts.
2. Reset phone
3. Remove iCloud account
4. Reset phone
5. Add email accounts
6. Reset phone
(So far, this is the rigmarole that the Apple support suggested; it did not fix the problem)
7. I then went into the email accounts: settings-->Mail,contacts, calendars-->Select Email account-->Account-->SMTP-->Other SMTP servers
I had a long list of servers here (this was presumably a legacy from email accounts I had added and removed over the previous life of the phone; I had done a restore from my 3GS when I got the 4S) and I deleted them all (except for the reference to the second email account).
This sorted the problem for me.
Hope this helps anyone following in my footsteps