I have two email accounts: Gmail and Zoho. Both are setup to check for new messages every 5 minutes. Both use IMAP. My Zoho email account can only retrieve new messages if I either: 1. Close Thunderbird and reopen it 2. Click the two computers icon in the bottom left corner in Thunderbird to go offline and then click it again to come back online and then click Get Mail If I manually click the Get Mail without going offline first no mail is retrieved. My Gmail account seems to retrieve mail without any problem (every 5 minutes as expected).