For some reason any emails I send from my iphone don't go into my sent folder. It has become a pain. I sometimes use my phone to send business emails and I'm not always sure if they have even sent and don't have a record of them.
The emails I send from my computer are in the 'Sent' folder on my computer and my iphone. It's only the emails that I send from my iphone that aren't in my 'Sent' folder on the iphone or the computer.
Server settings are the same as on my computer. It's just like my iphone doesn't save the sent emails.