The most usefull ability I have found in YAM is the ability to apply XPK compression libraries to folders.
This is so very helpful, especially when I need to keep e-mail that is text related and constant like fault logging information that is sent from users on my work network.
Under Outlook, these folders typically get to the 600MB mark.
Under my lovely AMIGA and YAM, they are around 45MB.
Mainly because they are just text generated from web pages capturing user info, but also because, each fault report has the same information so compresses easily.
I LLLLLLove YAM
Really well thought out program. Only feature I would love to see is some sort of RTF or HTML viewing, but I'll live without it for all the other features.