see NaN's response above, and also consider a common address structure of user@department.company.tld. This and other more complex structures are quite common.
As is stated much earlier in this thread (and learned through experience as a bitnet/usenet/campus email routing gateway admin), email addresses are not trivial. The localpart of addresses is oft horribly mangled or restricted ('-' in the $localpart converted to '_', case mangled from what is provided, etc). I treat the mangelings reasonably on my side, but the fact that they get mangled in the first place is irritating, and gives me pause when considering if the organization's IT department is up to the challenge. Since I seed addresses given to companies to identify spam leakage, I also eschew companies that restrict or mangle '-' and '+' when possible.
