I have thousands of the blasted things in my in-boxes.
Not so much of a problem if you use a web-based email account such as Googlemail, Yahoo, Hotmail or one of sundry others but if you have specific email accounts then the storage is on your system not some other server and when you reach the preset limit (which is pretty high) they start to delete the oldest.
What do VPers do with their emails?
Read, reply and delete
Read and leave in their system for future reference
Read, reply, print copies and file them ..... then delete
These seem to me to be the only available options and obviously the first is the sensible one but I was brought up in an age when one filed everything and I dread deleting anything that I may need at some time in the future. My main in-box is sub-divided into various files to enable me to keep track but even so I can never find anything more than a month or two old.