NOTE: There's a recent bug in Gmail that causes IMAP label changes to take a while before they take effect, so if you change the visibility of a label, it might not take effect in Mailbird for a while. Please see this for a workaround:
https://groups.google.com/forum/#!topic/google-mail-xoauth-tools/-vYQRDapR7U
Background
If you're experiencing problems starting Mailbird, IMAP access is most likely not enabled in Gmail or not all system folders are marked as visible through IMAP.Part 1: Activate IMAP in Gmail
- In Gmail, click on the gear icon top right of the screen to open the drop down list and then click 'Settings'.
- In the settings window, click on the 'Forwarding and POP/IMAP' tab at the top to go to that tab.
- In this tab, make sure that 'Enable IMAP' is selected.
Part 2: Make system labels visible through IMAP
Mailbird uses the Gmail system labels for various operations, to ensure a more seamless experience. Therefore it requires that all system labels except 'Chats' are shown in IMAP.
- Click on the 'Labels' tab at the top.
- In this tab, make sure that the far right checkbox 'Show in IMAP' is checked for all required system labels as shown in the screenshot below.