To migrate fr om Voyager to TB: create a backup, restore it with TB
Backups created by v4.0 can only be restored by TB v4.0, backups created by Voy 4.1 or higher can only be restored by TB v4.1 and highr.
Alternatively:
Install TB, tell it you want to use it it with encryption enabled (the first question when you run TB when it hasn't been run and installed before), select a mail dirtectory, copy Voyager's mail directory to the new one and you're done. Use the same password for TB as you did for Voyager, the password is the encryption key.
Same lim its with the version numbers as with the backups.
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