Sent Mail from Different Devices Not Sync'ing--Why?

Sent Mail from Different Devices Not Sync'ing--Why?

Emails sent from my laptop (MacBook Pro, 10.9.5) and my iPhone (9.2) are not showing up on my main (desktop) computer (iMac, 10.8.5), all using Apple Mail.app as a client.

This is true with both my IMAP email accounts.

Emails sent from my main computer are showing up on the other two.

Any idea why this is happening, and how to fix it?

/Mr Lynn