While some ISP's may support "appending" extra characters to your e-mail address "prefix", it is best to verify this operation before proceeding. It could be a + or a - or it simply could not be available. Popular MTA's like courier and exim have support for this, but again the ISP has to enable this support and document it for their users.

As for if this actually works, I do not know as I still use iChat.

Another option would be for owners of domain names. If you own your domain name and you use it for e-mail you should be able to set up an e-mail alias that you can use for each device. As an example, roger.mac@site.lan, roger.iphone@site.lan and roger.ipad@site.lan. These could all be aliases for roger@site.lan which is the one true e-mail address.

Any ways, I hope everyone sorts it out and finds a solution that works best.