Issue: Thunderbird Mail App Not Syncing

Thunderbird is one of the best email clients to access your IMAP or POP email accounts. Sometimes, the Thunderbird mail app not syncing on your email account and as a result, you won’t be able to access your latest email messages. In such cases, you have to check if all the settings have been configured correctly in Account Settings.

Server type

Most of the email service providers support IMAP (Internet Message Access Protocol). It is a fully featured mail delivery protocol when compared to POP (Post Office Protocol).

To find whether your email account uses IMAP or POP, navigate to the Account Settings window. Click the Server Settings tab in the left panel. In the main panel, go to the Server Type field and you will see either IMAP Mail Server or POP Mail Server. Configure the settings and fix the Thunderbird mail app not syncing.

IMAP

If you are using the IMAP server type, it has the following benefits.
It supports both online and offline activity. This indicates that you can store your email messages on your local computer as well as on the email server.
You can use multiple clients to access your email messages.
As already mentioned, you can access your older email message even without Internet access.
If you store your emails on a local drive, it will load faster. It is far better than searching your email messages on the remote (mail) server.

IMAP Sync in Thunderbird:

The functioning of IMAP sync in Thunderbird during various scenarios are given here to fix Thunderbird mail app not syncing issue.

Message deleted in Thunderbird: If you delete an email message in Thunderbird, it is deleted from both the local computer and the email server.
A message downloaded to Thunderbird and deleted in another email client: The email message must be deleted only from the Thunderbird message repository.
Saved draft message in Thunderbird: The draft must be copied to the email server also.
Thunderbird synchronizes with the email server when it is connected to the Internet. If the computer’s Internet connection is lost, you can still access your email messages that are already downloaded to Thunderbird.

Solution for sync issue in Thunderbird:

If you have a stable Internet connection, but the Thunderbird client is not synchronizing, perform the following steps.

Launch the Thunderbird client.
Go to Tools -> Account Settings.
Click the Synchronization & Storage tab in the left panel.
Navigate to the Message Synchronizing section and select the ‘Keep messages for this account on this computer’ option.
Note: If you have not selected this option, click the Advanced button and deselect the ‘Show only subscribed folders’ option.
Go to the Disk Space section and select the radio button beside the ‘Synchronize all messages locally regardless of age’ option.
Click OK to save the altered settings.
Close the Account Settings window.
Now, check if synchronization works properly in Thunderbird.
Finally, you fix the Thunderbird mail app not syncing issue.