Define the filter for one account, then copy the msgFilterRules.dat file in the account subfolder of ImapMail or Mail in the profile, into the subfolder for the other accounts (with TB closed). The Unifed Inbox or other folder is not an actual Inbox, but rather a kind of saved search, so filters can't be defined for it.

Thank you.

I have some rules which only make sense for an individual Inbox. So I cannot simply make all the msgFilterRules.dat files the same.

I was hoping for either (1) a set of "global" rules (applied before each Inbox's rules), or (2) a way to mark a given rule as applying to a number of Inboxes.

But I suppose cutting and pasting rule definitions from one msgFilterRules.dat to another may be easier, and less error prone, than entering the same rule for all Inboxes -- though, on the other hand, it it may be easy to scramble a msgFilterRules.dat file by messing with its innards :-(

Chris

25 years and counting: https://bugzilla.mozilla.org/show_bug.cgi?id=34973

If your filters have a long set of From conditions, note that it's often easier to add contacts to an address book, and then make a filter with From + is in my address book + <select an address book>. New contacts can be easily added to the specified book, instead of editing the filter.