As the title says, there are currently a couple email hosts that do not accept any emails e621.net is sending out, the list of known hosts that ignore our mail is currently:

• any hotmail server (.com, .de, .ca, .co.uk, ...)
• any live server (.com, .de, .ca, .co.uk, ...)
• any outlook server (.com, .de, .ca, .co.uk, ...)

If you wish to create an account be aware that you will not receive the account activation email and thus won't be able to complete your registration.
If you wish to reset your password be aware that you will not receive the password reset email which contains the key to actually reset your email.

We recommend using the multitude of other email hosts around (for example gmail.com or yahoo.com) to receive email, if you have an account already we also recommend switching the email over to another host until we can sort this issue out.
The option to change your email can be found here, it is the third block from the top of the page.

As always, if you can't access your account in the first place, either through forgotten password or missing account activation email, then be sure to check this thread out and otherwise email us at [email protected] and we'll help you as soon as possible.