Hello. I joined the forum to attempt to help with this issue. Hopefully I can:
NOTE: This applies to Outlook (specifically tested on Outlook 2003), NOT Outlook Express. Also, you MUST be using Outlook on the same machine every time.
There are at least FOUR issues combining to cause your "Random" disappearance. Postings to your message are touching on some of it.
1)AOL auto-deletes messages after a few days... read or not!
2)Outlook will read messages but not store them locally UNLESS you configure it to do so.
3)Outlook will auto-archive messages and delete them (well actually move them).
4)Outlook will store messages (and auto-archive them) to a file specific to the USER PROFILE being used. ALWAYS USE THE SAME USER PROFILE ON THE SAME MACHINE.
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THE GOOD NEWS is that if you solve #2, chances are you can retrieve even "disappeared" messages.
You cannot do anything about #1. AOL ALWAYS auto-deletes messages from your "New", "Old" or "Sent" tabs. There's nothing you can do about it, except add your name to everyone else that has asked them to change it.
In the meantime...
PICK ONE PROGRAM NOW. DO NOT USE BOTH AOL AND OUTLOOK, AT LEAST UNTIL YOU ISOLATE THE PROBLEM.
*** The MOST important thing you can do is to solve #2. Set your INBOX to "Download Complete Items Including Attachments" (Outlook: Tools > Send/Receive > Send/Receive Settings > Define Send/Receive Groups > Edit > INBOX > Download Complete Items Including Attachments > [OK] > [Close]). If you download only headers, you will have a similar problem... You will see the message in the list, but will not be able to open it. THIS WILL BE THE CASE FOR ANY IMAP MESSAGES.
(As an alternative, you can MOVE all of your inbox messages to a folder under your "Saved" AOL folders. Ironically, AOL will save user-created folders on the server indefinitely. This might be the easiest way to solve your problem without really determining what your problem was and also make them available to any Windows User Profile on any machine...maybe.)
Ignoring the parenthesis, if you perform the instructions above, and download as soon as you open Outlook (if you are not sure, just press <F9> to download), you will have A COPY of your AOL "New" and "Old" Messages in your Outlook Inbox even if you delete them from either program (Outlook "marks" them for deletion but does not delete them from the local file).
If you you have done this already and still have the problem, make sure you do the following TWO things: In your Advanced Tool Bar "Views drop-down" make sure you select IMAP Messages. This will show "deleted" messages with a "strikethrough" the list entry. If that is the case, righ-click on the deleted message entry and click on "undelete".
If you do not see the entry and it has "disappeared" after being downloaded to the local file, it means your Outlook "auto-archive" has kicked in and moved your message. Not to panic, you can open your auto-archive .PST file and access all your "disappeared" messages. To find your auto-archive file, you can see the auto-archive settings (global and specific to that folder) or do it the easy way by going to your Windows Explorer Star Menu > Search > For files or folders ... and search for files named *.PST in your whole drive.
I hope this helps. Please let me know.
Pablo Arriola
Pablo@Arriola.org