How to set the iphone mail app to send email only
You can setup iOS to send only, you just have to fool it :)

Here is how I did it on iOS 7...


If you have an existing GMail account setup in iPhone Mail, delete it.
Go to Settings > Mail, Contacts... > Add Account
From the list of choices, select Other
Select Add Mail Account
Fill in your details for your mail account, press Next
Choose POP instead of IMAP
For Incoming Mail Server I used dummy info like

Server: blah.gmail.com
User Name: blah

For Outgoing Mail Server I used the proper settings

Host Name: smtp.gmail.com
User Name: 
Password: 

Press Save

If it asks to save without SSL answer with NO

Press Save again!

It will warn you that it may not work. Confirm save.

Go to Settings > Mail,Contacts,... > 'your account' > SMTP > Primary Server
Verify SSL is on
Change Server Port to 587
Press Done and exit to Accounts.


That is it! You can now send emails and if you open the mail app it will complain because of the dummy Incoming Server.

Also check that you have the Settings > Mail,Contacts....> Fetch New Data settings to off/manual.

Hope that helped.