[quote user="Brian Fluet"]... A known solution is to use the Pegasus Mail Notsplit utility to generate message files from the .PMM for re-integration back into Pegasus Mail folders but what could the approach be when Pegasus Mail is not in the picture?  An obvious answer of placing the .cnm files into a mailbox directory isn't practical when there's hundreds if not thousands of them.[/quote]

I believe in that case you've got a problem. Also in case your server (where Mercury is running) or your accessing client is a 64bit system, any IMAP client wouldn't access the mailbox directly but always via the 32bit Mercury-I. And 32bit software can address max 2GB of RAM (except some special cases of 32 bit software which is able to address up to 4 GB). Don't know whether other (64bit) IMAP server are able to access Mercury/Pmail mailboxes? Maybe someone has tested it already?
I regularly check the mailboxes of my users and carry out a search for files larger than 1 GB. If I find something, the user get a message to remove big attachments or to create a new mail folder to avoid a further increasing.

We know about the 2GB file size limitation of folder files (.PMM files) from a Pegasus Mail standpoint but does this limit exist when access is via MercuryI by non-Pmail clients?

It applies to folders handled by Mercury as well. David commented it this way some time ago: "The largest folder that any of my programs can currently *manage* is 2GB, but because of the way they're manipulated, it's often quite possible for the file itself to continue having messages *added* to them once they exceed this limit. This is one of the things I have addressed in MailStore - legacy folders can no longer be expanded past the limit, and v5 folders using SQLite can be of any practical size and hold any practical number of messages."

Here's an interesting question.  Consider someone running Mercury with its IMAP module providing access to the mailboxes by non-PMail clients.  One of the folder files hits the 2 GB limit and can not be accessed.  A known solution is to use the Pegasus Mail Notsplit utility to generate message files from the .PMM for re-integration back into Pegasus Mail folders but what could the approach be when Pegasus Mail is not in the picture?  An obvious answer of placing the .cnm files into a mailbox directory isn't practical when there's hundreds if not thousands of them.