I have an archive copy of just about every email I’ve sent or received since about 1996, and certainly haven’t deleted an email since 1998 – not even the spam.  Many people know this – and many colleagues do something similar.

I suppose I have two reasons for doing this:

• trawling the archives is occasionally useful (for finding information, or confirming what someone said, or being reminded what I said); because just about all of my work is eventually mediated (in and out) by email, the mailbox archive plays the role of a professional journal.
• the process of filing and deciding what to retain and what to delete is insanely time-consuming, and easily costs more than the now insanely cheap cost of disc storage and associated backups.