Thunderbird

Interface

• To show the total number of messages in mailboxes / local folders (very useful), check View => Layout => Folder Pane Columns.

Gmail backup

• Follow this procedure:
  • Create a label in Gmail with all the data you want to backup / remove (for instance: Gmail 2016).
  • Label all the necessary messages with this label (the before:2016/01/01 filter may be useful). For a full year, "after: 2017/01/01 before:2018/01/01" (2017 example).
  • Launch Thunderbird, add your Gmail account via IMAP (if not already created). Get the previous backup files hosted in storage hard drives.
  • Create a local folder (named for instance Gmail 2016).
  • Select all the messages inside the new Gmail label, and Use "Copy the messages" to copy them to the local folder. This will take a very long time as all messages will be downloaded. To check if it is finished, compare the number of messages in the Gmail label and on the Local folder, they should be equal.
  • It is recommended to also copy them to another folder containing all mails from Gmail (named for instance Gmail - Total Backup). Before doing that, count the number of messages in the current Gmail - Total Backup. The operation is finished when the new count is equal to the old one + the number of new messages (in Gmail 20xx).
  • Once this is done, you can also easily create a file backup (of several GBs) of this folder just by copying 2 files (one without extension and one with .msf extension) on ~/.thunderbird/th3bio9j.default/Mail/Local Folders/ to somewhere else.
  • At last, put all messages on the Gmail label to the Trash and empty the trash.

• Note that if you move the messages with Thunderbird (to a local folder), they won't be deleted on Gmail. By default Gmail archives them which just means the "Inbox" label is removed.
• It can be useful to visualize storage used on Google (per app) at https://one.google.com/storage.

Other notes

• It's better to always keep the "Gmail - Total Backup" local folder available in the current Thunderbird directory, so that old mail messages can be searched via Thunderbird.
• Selecting messages and right click -> Get selected messages does not seem to work. "Get selected messages" is always greyed out. Thunderbird normally downloads just the headers of messages and not the actual content. However copying the messages to a local folder forces the application to download the content as well.
• It does not seem needed to put Thunderbird in offline mode. In offline mode Thunderbird cannot copy the messages from the Gmail label to the local folder.

Directories on disk

• Thunderbird directories are on ~/.thunderbird/th3bio9j.default/ (th3bio9j is the proile ID). Local folders are on ~/.thunderbird/th3bio9j.default/Mail/Local Folders/.
• On Windows, the folders are on ~/AppData/Roaming/Thunderbird/th3bio9j.default/Mail/Local Folders/.

Plugins / Addons

The Import/Export tools is able to export Thunderbird mailboxes to different formats.