Before replacing a computer: prepare a Thunderbird profile backup

Use this for your own Thunderbird desktop profile before a computer replacement. Prepare the backup scope and route; successful restoration and permission to erase the old computer remain unresolved.

Choose the material and destination

Mozilla’s Export guide describes a ZIP containing the current profile’s accounts, messages, address books and settings. Choose this broader scope deliberately.

The profile guide, profile location and backup sections, explains that profiles also contain passwords and preferences, separately from the application. Use Thunderbird’s troubleshooting information to locate the actual profile; copying the program folder is not this backup. Keep the profile out of public attachments and feedback.

Choose the size route

The Export guide supports ZIP backups up to 2 GB. For a profile larger than 2 GB, it directs manual copying of the whole profile to an empty destination folder. Resolve unknown or ambiguous size before choosing.

The ZIP route is Tools → Export, then export, choose destination/name and save. For a manual profile copy, the profile guide requires closing Thunderbird first. Record which route is intended and which application version/profile it concerns; no copy has been created by this preparation.

Check the local-mail gap

Mozilla’s IMAP explanation, synchronization and storage sections, distinguishes locally downloaded bodies from headers-only messages. A visible message list therefore does not establish a complete local mail copy. Subfolders are not automatically synchronized just because their parent is selected, and age/size settings can limit downloads. The page is dated October 27, 2015: use this as a coverage question, not a promise of today’s control layout. Do not change synchronization settings or delete mail as part of this preparation.

Hand back the intended profile, route, private destination and unresolved local-content questions. Keep actual contents, readability and restoration as separate checks before any retirement decision. A filename or completion notice is not evidence that the requested records are recoverable.

Evidence: Three official Mozilla pages read through 2026-10-05T17:57:07Z. Export is dated March 11, 2025; Profiles September 13, 2025; IMAP as above. Sixteen synthetic manual decisions checked this preparation; no profile, account, export, copy, synchronization, restoration or erasure was accessed or performed. A distinct same-controller checker reopened all three sources and checked the sixteen author decisions plus eight additional manual boundaries at 2026-10-05T18:04:13.364276Z; shared control supplies no independent formal coverage. Recheck changed versions, storage scope or guidance before use and by 2026-11-05T17:57:07Z. Report unclear branches without private profile contents. Follow the email-intake standard [current article].