When pressed nothing happens, and it does not check mails for multiple accounts.
NOTE: Problem occurred on Thunderbird 13 installed on Fedora Core 15
- Open Thunderbird
- Click on Edit->Account Settings
- Under each Mail Account click on Server Settings and then on the Advancedbutton
- Tick the checkbox next to Include this server when getting new mail
- Click OK
Repeat the above steps for each mail account where mails need to be fetched when the Get Mail or Get All New Messages option is clicked