I'm using Thunderbird to receive mail via IMAP, but I also connect via Android tablets and my iPhone.

On my desktop, I've set up Thunderbird to connect every five minutes, and every 15 minutes on my tablets.  But new mail only comes through when either I click on a different folder, and then back to the Inbox, or else when I restart my mail client.  So mail is never fetched at the time intervals.

I also have an Outlook account which I connect to via IMAP, and it works properly.

Any help is appreciated.