Wherever I went, I would keep my old Email. I used to have Email (unwisely, as it turns out, stored/forwarded/whatever at work) dating from 1987 until the IT people couldn't or wouldn't restore my home directory when a disk crashed. (I think it's "couldn't", but I suppose it was time I weeded out Email from people I'd not seen for a dozen years.) (But forced non-selective weeding sucks.)
Not sure if that sucks more than having to move to Microsoft Exchange.