Steve Jones - SSC Editor (8/28/2014)
It's tough, as Troy Hunt found out.http://www.troyhunt.com/2013/11/dont-trust-net-web-forms-email-regex.html
Honestly, it's good to try to validate, but don't discard data that doesn't meet the standard you set. It's highly likely your validation is broken. Even if you say "it's all North America", people move all the time and you might end up with foreign items over time. Or your company expands.
Throw suspected items into a queue and have someone review them. Contact the person. If you do this in a front end form, give the user a way to bypass validation and give their email with a captcha or some other type of "human" validation that their email is correct.
This seems sort of directed at me.
The email addresses I was processing were not from a web form, they were provided to us either by clients, or by data marts. Nothing was deleted, it was just given a 'status flag' that meant the email inspection found something wonky. A certain percentage of the contact information was expected to be inaccurate or incorrect. So if the project was running a long time without a high response rate, and the PM didn't want to buy more sample, the remainder email addresses could be released.
I had to do a lot of similar stuff with phone number cleaning/checking and formatting so the dialer could make the calls correctly.
Market research is a bummer.
*shrug*