Freron MailMate

Hi,
Ive been using MM for years with mail files saved on an external volume, which I connect to using the 'Custom Location' option.

That volume crashed recently, and we've replaced it with a new volume, and restored all our MM files.

BUT - when I launch MM, it tries to find files on the OLD volume, and displays a message "Mailmate failed to save a volume to disk".
Its trying to find files on the OLD volume, and cannot - which makes sense.

The problem is that I cannot reset the preferences for the 'Custommm Location' from the MMM preferences pane.

When the error message pops up, the Preference Pane is not available.
and when I click 'Retry' to dismiss the error message, MM immediately tries to save the file again and the message reappears,
giving no time to update the MM preferences to specify the new Custom location for all the MM files.

Ive tried deleting the file /user/library/ preferences/com/freron.MailMate.plist - but that doesn't help.

What can I do tp reset the Custom Location ?

Thanks,

Gary