Find the folder

1
In Thunderbird, open Help → Troubleshooting Information.
2
Next to “Profile Folder”, click Open Folder (Show in Finder on a Mac).
3
Open Mail, then Local Folders. Mail of IMAP or POP accounts kept on this computer is under Mail/<server name> or ImapMail/<server name>.
4
Before importing, run File → Compact Folders and close Thunderbird, so the files are complete and messages you deleted are really gone.

Import

1
Open Import files and press “Choose a folder”. Pick Local Folders (or the account folder).
2
Each file without an extension (Inbox, Sent, Clients) becomes a folder; subfolders inside Inbox.sbd keep their place, so Inbox.sbd/Clients becomes Inbox/Clients.
3
The .msf files next to them are only Thunderbird’s indexes and are ignored.

What comes across

Read and unread, replied, starred and Thunderbird tags (as IMAP keywords), and the date each message was received. Messages Thunderbird marked as deleted but had not compacted yet are left out.

If the old account is IMAP and still works, a server-to-server migration is simpler and copies everything, including mail Thunderbird never downloaded.

Is this guide useful?

Find the folder

1
In Thunderbird, open Help → Troubleshooting Information.
2
Next to “Profile Folder”, click Open Folder (Show in Finder on a Mac).
3
Open Mail, then Local Folders. Mail of IMAP or POP accounts kept on this computer is under Mail/<server name> or ImapMail/<server name>.
4
Before importing, run File → Compact Folders and close Thunderbird, so the files are complete and messages you deleted are really gone.

Import

1
Open Import files and press “Choose a folder”. Pick Local Folders (or the account folder).
2
Each file without an extension (Inbox, Sent, Clients) becomes a folder; subfolders inside Inbox.sbd keep their place, so Inbox.sbd/Clients becomes Inbox/Clients.
3
The .msf files next to them are only Thunderbird’s indexes and are ignored.

What comes across

Read and unread, replied, starred and Thunderbird tags (as IMAP keywords), and the date each message was received. Messages Thunderbird marked as deleted but had not compacted yet are left out.

If the old account is IMAP and still works, a server-to-server migration is simpler and copies everything, including mail Thunderbird never downloaded.

Is this guide useful?

Import Thunderbird mail folders into a new mailbox

Find the folder

Import

What comes across

More importing saved mail guides

Import Thunderbird mail folders into a new mailbox

Find the folder

Import

What comes across

More importing saved mail guides