At most, MW's installer should verify the email address is valid, but I'm not even sure of that. It would be good to add a warning about potential pitfalls if the email address isn't valid, though.

If you need to set the email sender see $wgEmergencyContact and/or $wgPasswordSender.

imz wrote:

I'm collecting the cases of such pitfalls at http://en.altlinux.org/Non-delivery_of_email_sent_by_automated_services_to_altlinux.org . Just in case someone is interested in turning sysadmins' attention to this problem, too, and will at least make the sysadmin and all people aware of such sites publicly. It's quite annoying to come across such a site (whose emails don't get through to you).

Not only MediaWiki is one of the popular software that often has a bad sender for the outgoing emails, but Bugzilla is, too.