I've never used Mail but I assume it can either natively use or easily import Eudora-format mail files (which are industry-standard give or take line endings). Do you have FileMaker? QuicKeys may be available on a try-before-you-buy basis for OS 9. QK is necessary because AOL is not sufficiently AppleScriptable (you would need to declare a variable and set it to the contents of each email in turn; and since you can't do that, you need to tell it to copy each email to the clipboard in turn, which it can't do either but which can be automated, along with "go to next email", as a series of clicks and keystrokes via QuicKeys, which as long as it's being deployed may as well boss FileMaker around too.
FileMaker comes into play most centrally for parsing the text block that comes in from AOL, separating out the Date, From-header, To-header, and Subject line, and adding the other (usually hidden) headers with boilerplate and/or calculated defaults for their values. Then the whole database is exported, using just the calculated text field containing all the fields with their fieldname headers and returns and dividers between messages and whatnot inserted.
I think it requires a final massage in BBEdit (or TextWrangler) to substitute real returns for the vertical-tab used by FileMaker for a return within a field — not sure of that.
Anyway, assume you extract from AOL PFC the From-header, To-header, Subject, and Body of a given message (using QuicKeys I automated the tabbing from field to field and copying and pasting into waiting FileMaker fields), here's the formula for converting each individual email to Eudora (.mbx, industry-standard, blah blah blah) format:
"From ???@??? "&Left(DayName(Date), 3)&" "&Left(MonthName(Date), 3)&" "&Day(Date)&" "&"01:24:32 "&Year(Date)&"¶"&
"Status: U"&"¶"&
"Return-Path: <yourAOLaddress@aol.com>"&"¶"&
"Received: from anyname@isp.net ([111.111.111.111])"&"¶"&
TabChar&"by something (SomeISP SMTP Server) with ESMTP id tss3ek.cfq.37tiu0o"&"¶"&
TabChar&"for <anyname@isp.net>; Wed, 17 Oct 2005 16:01:40 -0700 (PDT)"&"¶"&
"Received: from [195.206.50.162] (50-162.ppp.dsi.ru [195.206.50.162])"&"¶"&
TabChar&"by mail.blah.com (8.12.0/8.12.0) with ESMTP id f9HN1YSU026437"&"¶"&
TabChar&"for <anyname@isp.net>; Wed, 17 Oct 2005 16:01:38 -0700 (PDT)"&
"Date: "&Left(DayName(Date), 3)&", "&Day(Date)&" "&Left(MonthName(Date), 3)&" "&Year(Date)&" 12:37:32 -0700 (PDT)"&"¶"&
"From: "&AOLMsg FROM&Case(PatternCount(AOLMsg FROM, "@")=0, "@aol.com")&"¶"&
"To: "&AOLMsg TO&Case(PatternCount(AOLMsg TO, "@")=0, "@aol.com")&"¶"&
"Subject: "&Subject&"¶"&"¶"&
Email Body&"¶"
The QuickKey macros are along the lines of:
{assumption is that you have AOL open, offline mail open, first message selected; you have to run Mail Sent and Mail Received separately; you also have FileMaker open, with a layout with AOLMsg TO and AOLMsg FROM and Subject and Date on them; TabChar is a global field containing a tab character} {count the number of msgs in the AOL mailbox and enter into the repeat counter of QuicKeys when you first trigger the macro}
Repeat x Times {specify on run}
Switch Process to AOL
Hit Return
Wait 0.2
Tab
Copy
Switch Process to FileMaker
Command-N (new record)
Tab
Paste
Switch Process to AOL
Tab
Copy
Switch Process to FileMaker
Tab
Paste
(etc for all fields)
Switch Process to AOL
Command-W (close current email msg)
Down-arrow (go to next)
End Repeat