This can speed things up, but these messages still consume hard disk space.

Compacting is the process of totally deleting these marked messages, clearing space in your inbox.

Here’s how to compact folders in Mozilla Thunderbird, both manually and automatically via options.

Compact folders highlighted in Thunderbird File menu

How to Compact Folders in Mozilla Thunderbird

SelectFile>Compact Folders.

Here’s how:

SelectThunderbird>Preferences.

Scroll down toCompact folders when it will save over_MB, and put in your desired disk space threshold.

Thunderbird Preferences highlighted in menu

ClickI accept the riskif prompted.

Double-clickmail.purge.askunderPreference Nameto toggle its setting (visible under Value).

Close theabout:configpreferences window and selectClose.

Compacting options in Thunderbird

If you find messages missing or deleted emails appearing after compacting your folders,rebuild or repair their indices.

Config Editor button highlighted in Thunderbird

Thunderbird warning screen

Thunderbird about:config

mail.purge.ask in Thunderbird about:config