Recover a missing or inaccessible Thunderbird profile
What to do first
Repair Thunderbird’s profile location and default selection without deleting mail data.
This is a general troubleshooting guide, not an announcement of a current outage.
Affected products and symptoms
- Product
- Mozilla Thunderbird
- Versions and conditions
- Thunderbird Desktop on Windows, macOS, and Linux
- Error codes and identifiers
- thunderbird -P
Symptoms
- Thunderbird says the profile is missing or inaccessible
- Accounts and mail appear gone after an update or move
Causes and conditions
A moved or renamed profile, mismatched profiles.ini entry, permissions, or selection of a different profile are typical causes.
Before you start
- Fully close Thunderbird and copy the profile folder to another drive
- Record folder names, dates, and sizes under %APPDATA%\Thunderbird and Profiles
Precautions
- Profile Manager’s Delete Files action cannot be undone
- Do not use one profile concurrently from multiple computers
Step-by-step instructions
On Windows, enter %APPDATA%\Thunderbird\Profiles in File Explorer. Check ~/Library/Thunderbird/Profiles on macOS or ~/.thunderbird on Linux.
With Thunderbird closed, copy the likely profile containing Mail, ImapMail, prefs.js, and substantial data to a separate local location. Cloud sync alone is not a backup.
Close Thunderbird and run thunderbird -P from Windows Run. If it does not open, end remaining Thunderbird processes in Task Manager and retry.
When Thunderbird opens, Menu > Help > Troubleshooting Information > about:profiles also manages profiles. Specify the full executable path if several installations exist.
Choose Create a New Profile > Next, give it a clear name, then use Choose Folder to select the preserved existing profile folder.
Select only the profile folder. Choosing an unrelated non-empty folder risks losing its contents if Delete Files is used later.
Select the recovered entry and Set as default profile, or enable startup prompting. Open offline first and inspect accounts and local mail.
There is no need to remove the empty profile. If you remove an entry, choose Don’t Delete Files first so its data remains.
Confirm the folder tree, Local Folders, and address book, then go online and receive one account at a time.
Mozilla does not support simultaneous access to one profile over a share or cloud storage; it risks corruption and permanent data loss.
Check the result
- Previous accounts, folders, and address book appear
- The recovered profile remains the default after restart
If the problem continues
- Create a clean profile and migrate only required data in stages
- Restore a missing folder from backup or the synchronized mail server
Scope of this guide
Troubleshooting guide — Preserve the profile data, then select or register it in Profile Manager and correct an accidental switch to an empty profile.
Frequently asked questions
Will reinstalling Thunderbird restore it?
The profile is stored separately from the program. A broken reference often survives reinstallation.
How do I identify the old profile?
Do not rely only on dates. Check size and the presence of Mail, ImapMail, and prefs.js, then copy it before changes.
Official sources and dates
- Profile Manager - Create and remove Thunderbird profiles | Thunderbird Help ↗
- Profiles - Where Thunderbird stores your messages and other user data ↗
Source publication or resolution date: Not specified. Sources checked: 2026-09-05. The check date is not the date the problem first occurred. Interface labels can vary between versions and display languages.
Related troubleshooting guides
- Fix Thunderbird when receiving works but sending mail fails
- Rebuild Thunderbird’s global search index when results are blank or slow
- Fix Acrobat “A running instance has caused an error”
- Fix Firefox “already running” or profile-in-use errors
- Identify the source of Chrome “Managed by your organization”
- Fix OneDrive “Can’t open file” or “Make sure OneDrive is running”