Email "Sent" Folder Syncing Issues (Mac - iPhone)

[jonsm]

Hi, I just configured a friend's Mac so that he is using the Mac's "Mail" program for his iCloud email address, as well as a custom domain email account. I set up his iPhone 5 to do the same.

However, the "Sent" folders don't seem to sync properly for the non-iCloud account. On the Mac, he ends up having two different Sent folders, one under the email account folder and another listed at the bottom on the left. The one under his account lists sent messages from the Mac. The one listed further below lists sent messages from the iPhone.

Meanwhile, on the iPhone, I had noticed two "Sent" folders, one called "Sent" and one called "Sent Messages". The latter seem to contain anything and somehow I made it disappear. The former, "Sent", did contain sent mail from the iPhone but not from the Mac.

Any thoughts on how I might fix this?

Thanks in Advance!

 

[jonsm]

Screenshot for further clarification

I have attached a screenshot from the Mac's "Mail" program (modified to remove personal info) to hopefully make it clearer what is happening. Again, in the Mail program I'm seeing two Sent folders, one containing the Mail program's sent emails and the other containing the iPhone's sent emails. On the iPhone, the sent folder only contains the iPhone's sent emails and I cannot see the Mac's sent emails. Ideally I would have one Sent folder on each platform showing all sent messages but I'd be happy if the iPhone could somehow show the Mac's sent emails. Thanks!

BTW, the Mac is running 10.9.5. The iPhone is running 8.4.1.