[Users] Disappearing sent mail

[Cliff Laine]

Hello, I've had to do a complete new install of Elementary OS and
things are going a bit odd with a couple of my IMAP accounts.

I have the option in Preferences > Advanced to "Save outgoing mail in
[the Sent folder]."

When I send anything using IMAP, the message just disappears into the
ether. It's nowhere to be seen.  It arrives at the addressee, but
obviously I need copies of what I've sent. This is happening on
accounts with mail.com and with 123-reg.co.uk.  Could anyone suggest
what might be happening?

Thank you 

Cliff

CM 3.11.1
KDE 4.14.2