[Justa]

I assume you're talking about Outlook, not Outlook Express. In Outlook mail files are kept in .pst type files. You can do a search, identify them and back them up before cleaning out your Deleted Items and Sent folders. You'll have to know or learn how to map .pst files in Outlook. Some people will have several .pst files due to their use of Personal Folders.

I recommend backing up .pst files to magnetic media such as a tape backup (expensive) or flash RAM (inexpensive). The latter can be done via a USB connection and a 'thumb' type drive so it's quite convenient. Just be sure to use a device with removable memory cards so they can be stored in an electrostatic bag off site. I would not recommend CDs. Most CDs degrade within 3 years.

Nowadays E-mail is business transactions and receipts so having a reliable long-term records is important imo.

[Publius6961]

I would not recommend CDs. Most CDs degrade within 3 years.

Could you please elaborate on this?
We have this discussion about once a year and I have not seen any recently.

All media deteriorate, but CDs are so ubiquitous now and people rely on the writeable ones so much that is deserves a current discussion.