in reply to
recommended storage format for email messages?
Your requirement that ...there is no need to use any 'mailbox' formats... is, AFAIK, of no consequence since the single file storage format is a function of sendmail - mail readers know that the e-mails in the mailbox file are stored as sequential ASCII text blocks - at least on *NIX anyway.
I don't know and care less about the format used by Lookout (errrm, Outlook)/Exchange - but I dare bet it's in some weird proprietary binary format...
A user level that continues to overstate my experience :-))