Best E-mail Archiving system?

I’m running into various issues when I try to use DTPO to archive my e-mail from Apple Mail and am hoping someone can share how they do it.

What I want is a separate DTPO database that contains my e-mail archive with all the sub folders as a backup that is more readily searchable than even the Apple Mail system.

I have a bunch of separate e-mail accounts, all POP that feed into a single inbox. I have a number of separate mailboxes that stuff gets filed into, some automatically by using mail rules and some I move there. Each e-mail list has it’s own mailbox for all list messages. I also have one for orders I am waiting for and orders received, one for each organization I am an officer in and one huge folder for Reference that contains every message rcvd that I keep.

I created a new DT database, selected File:Import:E-mail and selected the On My Mac icon. The checkboxes for hide Imported, Deleted and Junk are selected. Then I selected Archive Mailbox from the bar in the window.

This appears to work to get the received messages but I can’t get the sent messages unless I go into each mailbox for each mail account and import it separately.

Also it takes a very long time each time I run archive mailbox while the system figures out what was already imported and what is new.

Is there any way to sped up the archive process to avoid the long time it takes to figure out what is already there?

Is there any way to get the sent messages in a single sent mailbox like Apple Mail shows?

Why are the message counts within the DT database and the window for import different no matter what I try to do to get them the same? Am I really missing messages and I don’t know it?