Why is it important to do email verification upon sign up and is it "mandatory"?

Question

More than a handful of websites don't require registrants to verify their email and they seem to work fine without obliging you to go through this (minor) ordeal.

It seems logical this mechanism would assure email validity and would deter a robot non grata, but is it pertinent for a low user functionality website, for example, only for writing comments or anything relatively harmless like that, to enforce it?

Answer 1

It's crucial for the "forgotten password" scenario. For example:

1. User signs up
2. Accidentally makes a typo in their email address
3. Three months later, forgets password
4. Uses the "forgot password feature"
5. You're screwed

If you had checked the email in the first place, you'd be able to do the "best practice" at this point, namely, send a password reset link to their email address. (You're not actually going to send them their password. This would imply that you had stored their password. This would be a most severe security flaw, but that is not the topic at hand).

Email verification insures that you have an email path to reach the user in this situation (at least, until they close that account...)

Answer 2

Some great reasons are already covered: Let me try some more...

1) If you're going to use the email addresses, email verification can help you stay clear of being labeled a spammer. How? If too many of your emails bounce (I guess more than 2%), the sender and receiver email systems think you're a spammer.

2) If you continue emailing to email addresses where a lot of people don't open your emails you're spending money in (a) storing the email addresses, and (b) sending emails.

3) Your metrics won't come out right if an unusually large number of email addresses are incorrect. A blog I quote often explains the benefits more succinctly -

here's the link to the blog.