Outlook and lost sent emails

I am using Outlook for my Gmail. When I send an email I can see that it is in the "outbox" but when it is actually sent, it disappears. I have searched all folders but can't find it.

Going to the Gmail appIication I can find it in the "sent" items and if I file it in a folder then I can see the mail also in the outlook app (in the respective folder).

Can anyone help with this issue?

Thanks

rk