That is corrected in the user support documentation https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_restoring-to-a-different-location

How old is your windows 11 install? Have you cleaned up %temp% ?

Thank you for the question, Wayne. Windows 11 was installed 2/‎18/‎2025, and I've used the Storage Management any number of times to delete temp files. I've also uninstalled some apps I don't use, like Windows Office.

I have a ton of emails in Mozilla. It seems that what is running out of room is the Roaming data, on C drive. Not just the profile, but I'd like to move all of Mozilla's functions to the App drive (D:); data is on E:

You can install Thunderbird program wherever you choose.

For example: In D: drive create a folder called 'Program Files' In 'Program Files' create a folder called 'Mozilla Thunderbird' So you have D:\Program Files\Mozilla Thunderbird

Uninstall Thunderbird and get a fresh download from : https://www.thunderbird.net/en-US/thunderbird/all/

When it starts the install you will a prompt which says it will install in default location, but there is an option to install where you like: click on 'Custom' and choose D:\Program Files\Mozilla Thunderbird folder

AS for the Profiles you could do this: In D: drive create a folder called 'Thunderbird' So data will get stored in D:\Thunderbird

Exit Thunderbird if it's running.

• In Windows search type: %Appdata%
• select %Appdata% file folder
• Select 'Roaming'
• Select 'Thunderbird'
• Copy the 'Profiles' folder

• Access: D:\Thunderbird
• paste the 'Profiles' folder into 'Thunderbird'

Back in Appdata\Roaming\Thunderbird Important: Copy the 'profiles.ini' file to desktop to act as a temp backup - just in case required.

Open the 'profiles.ini' file using a simple text editor eg: Notepad

You need to edit the 'profiles.ini' file to point everything to look in the new location. Example: [Profile0] Name=default IsRelative=1 Path=Profiles/cba4d602.default Default=1

change 'IsRelative' from 1 to 0 (zero)to: Change 'Path' to say new location of stored data and remember to alter the slashes from / to \ [Profile0] Name=default IsRelative=0 Path=D:\Thunderbird\Profiles\cba4d602.default Default=1

also look for any install numbers with same profile name and alter location. example: [Install39562346F8DE8E50] Default=Profiles/cba4d602.default Locked=1

[Install39562346F8DE8E50] Default=D:\Thunderbird\Profiles\cba4d602.default Locked=1

Then save the file.

When you start Thunderbird, access the 'Account Settings' > 'Server Settings' for each account and check it is pointing to correct location of account name that stores data. example:

• Local directory: D:\Thunderbird\Profiles\cba4d602.default\ImapMail\imap.gmail.com

Remember to also do the same for the Local folders

• Local directory: D:\Thunderbird\Profiles\cba4d602.default\Mail\Local Folders

Then you can delete the original profile name folders

• In Windows search type: %Appdata%
• select %Appdata% file folder
• Select 'Roaming'
• Select 'Thunderbird'
• Select 'Profiles' folder

Until proved all works ok - Move the actual profile name folders onto desktop, so Profiles is now empty.

Exit and restart Thunderbird - if all goes ok you can then delete those redundant profile name folders on desktop OR better still - put them onto an external drive as a backup.

What does all the above mean: The 'Roaming'/'Thunderbird' folder containing the 'profiles.ini' file and the empty 'Profiles' folder plus a couple other files will remain in situ. It does not use much in size. But the bulk of data has now moved to the D: drive.