Archive your emails in Thunderbird

Thunderbird can store your old emails in an archive folder of your choice. Archiving is done on demand: you select the messages and click Archive, and Thunderbird moves them to the configured folder and sorts them according to the options you chose.

In short: in Account Settings, under Copies & Folders, click Other and choose your archive folder, then select the emails and click Archive.

Prerequisites

Thunderbird installed and at least one email account configured.

How do I configure the archive folder?

Create, in Thunderbird, the folder that will receive your archives, for example under Local Folders so that archived messages are stored on your computer.

Thunderbird: right-click menu on Local Folders, with the New Folder entry outlined

Thunderbird New Folder window: folder name entered, the parent folder Local Folders is outlined

Open Account Settings.
Under the relevant account, select Copies & Folders.

In the message archiving section, click Other and choose the folder you just created.

Account Settings, Copies & Folders: Keep message archives in, Other and the chosen archive folder are outlined

In the archiving options, select the options that suit you. We recommend checking the box to keep the folder structure, as well as sorting by year.

Archive Options window: yearly archived folders selected, the keep folder structure box outlined

How do I archive messages?

In the email list, select the emails you wish to archive and click the Archive button.

Thunderbird message list: seven messages selected, the Archive button is outlined

For the official procedure, see the Archived messages page of Mozilla Support.

Going further

Set up an email account in Thunderbird, to set up the account in Thunderbird first.
Choose between IMAP and POP, and understand the role of SMTP, to understand why local archiving frees space on the server with IMAP.
Mailbox full: increase the quota of an e-mail address, to raise the quota instead of archiving.