I've been a believer that we need more than one SMTP address. The username version should be limited to email@example.com however, since you don't want to expose your usernames to the planet through email addresses. Then also have a firstname.lastname@example.org for Internet usage. If there are conflicts on the latter, I've been a fan of asking the user what they want.
Email addresses are somewhat personal, even if they're work/university email addresses.
I didn't like my email address at work, so I asked to change it. Standards, be damned!