Freeing up space on an iPhone 4S

[OTCHRussell]

A friend's iPhone 4S only has 8 GB memory. He only uses it for emails and as a phone and he was notified that he was out of memory.
I checked his storage and it said he was using 2.0 GB for mail. All other apps were not using much. I deleted all his emails, trash, inbox, sent, everything. It still says 2 GB and he has no available memory. I also restarted the phone.
Am I missing something? He is on IOS 8.3 and can't update. Other than getting a new phone, what should he do?

 

[anon(4697585)]

Restore the phone and start again. As it's only email it won't take long to reconfigure.
Remember to back up though

 

[OTCHRussell]

Restore the phone and start again. As it's only email it won't take long to reconfigure.
Remember to back up though

Thanks. We do have to make sure his contacts are backed up. Appreciate your help.