Everything You Need to Know About Thunderbird Sync Two IMAP Accounts

Jaspreet Singh | July 20th, 2018 | Email Server

IMAP is an acronym for Internet Message Access Protocols. It facilitates an email client to avail messages saved on the email server. It is more advanced and contains more feature as compared to POP i.e. Post Office Protocol. Most of the email service providers are now compatible with IMAP. To know whether a particular account is configured as POP or IMAP, go to Account Settings followed by Server Settings page. Also, refer the below-mentioned blog for better understanding the process of Thunderbird sync two IMAP account.


Advantages of Using IMAP

IMAP Server account is in harmony with offline and online activity. This implies that the messages can be saved on the server as well as the local machine. This results in many possible benefits:

  • The messages can be accessed using multiple email clients.

For instance, A Thunderbird user with MS Live account can utilize both the applications, that is installed on the system and a web-based interface provided by Microsoft.

  • In Mozilla Thunderbird, users can download their messages and save them in the local machine. These messages can be accessed even in the absence of proper internet connectivity.
  • Loading of messages is faster when they are saved on the local drive. Also, the search operation is faster as compared to searching messages on a server. Full-text search of any message is possible only when that specific message has been downloaded.

To avail these benefits, flexibility, and functionality, messages should be synchronized between the email server and the local machine.


To know about message synchronization, go through the following situations:

  • If a message is downloaded to Thunderbird and then, deleted. It will be removed from the local system as well as the server machine
  • A message is downloaded to the Thunderbird and then, later deleted by any web-based email application, for example, Yahoo Mail, Gmail. Then, this message will be deleted from the message repository.
  • A draft message, which is created and saved, but not sent in Mozilla Thunderbird. Then, the draft is copied from message repository to the mail server.

When Mozilla Thunderbird launches, it examines the status of synchronization between the email server and Thunderbird message repository. Then, it performs all the necessary migration like downloading fresh messages from the local server, deleting the message from the server that is already being deleted from the local system, etc.

Mozilla Thunderbird continuously synchronizes with the server until the time it is working and has a good internet connection. In case, internet connection is lost, Thunderbird will sync after the internet connection is reestablished.

Messages that are not synced can be still accessed within Thunderbird. The only difference is that only “headers” of the messages are downloaded. The body of the message is not downloaded until the user clicks on the message in the message list. It means, if a user is offline, he/she is unable to read the message.

Synchronization influences disk space usage and performance.

Performance and Search

As already discussed, messages stored locally load faster than the messages saved on the local server. If a message is saved on the local server, its body will not be downloaded until a user clicks on that message in the message list.

So, before Mozilla Thunderbird displays a message, it should be downloaded from the mail server.

In this scenario, if Thunderbird has to save a large number of messages from the server, it can cause temporary performance lag. The partial reason is the download process itself and also caused due to the indexing process. In the indexing process, the text of the message is examined and indexed, which enables rapid and impressive message search.

After the process of downloading and indexing is done, performance returns back to normal. The status of synchronization is shown in the bottom left-hand side corner of Thunderbird.

In Mozilla Thunderbird, an option of full-text message search is only present for the downloaded or synchronized messages. For non-synchronized message, only message header can be seen.

Disk Space Usage

If users have a lot of emails, and there is a storage space impulsion on the local drive, they may not want to sync all of the messages. As discussed above, headers can still be viewed. However, messages can be downloaded only when users are online.

Configuring Synchronization and Storage Space Usage

  • In the Account Settings dialog box, launch synchronization and storage page.

  • At the top of the page, select the option of Keep message for this account on this computer, if you want to sync messages between the local system and mail server
  • In case, this option is deselected, individual folders are to be synchronized. Hit on the Advanced button

  • The folders which are checked will be synchronized. Subfolders will not be synced automatically. You have to select each nested folder manually
  • General disk space settings will be configured in the lower section of synchronization and storage page. You are permitted to select general synchronization preferences.
  • There are other different options for deleting multiple messages in a single step, etc.

Final Words

IMAP facilitates an email service provider to access messages saved on the server. Another major protocol for acquiring email messages is POP. IMAP is more advanced and provides more features as compared to POP. In the write-up, complete detail is given regarding syncing two IMAP accounts.