compacting has nothing to do with compressing anything, so if that is what it says then there is a translation error.

From the file menu select compact folder and just get it over with in a single session. I suggest set it going and go home or go to bed. With anti virus intervention it might take another from a few minutes to hours. Depending on the amount of mail and the number of folders.

It may be due to my translation that it does not present the window's msg correctly. Sry.

Anyhow, the window is annoying and I can't see information why I have to click "OK". But I have to as there's no progress otherwise.

IMO it will support email handling velocity when the first of this type of msg comes with a toggle "progress without halting for further warnings of this type in this session" or so.

After all: thanks Matt for you reply.

you can control the frequency of compacting on preferences >menu > preferences> and search for Compact

I have mine set to only trigger when there is 11mb of deleted mail that needs removing from the folders, but you can set it higher, just be aware that mail is not really deleted until a compact occurs to remove it from it's original folder.

sounds like a useful solution. thanks Matt