Client: *Signs Up* We didn't receive email notification
Me: Okay, we'll check.
*checked if a sign up record is saved*
*checked logs*
*everything is working*
*checked mailing statistics, found 1 email bounced*
...
Me: Are you sure you're using the correct email address?
Client: *tried to sign up again*
Me: *monitors database record, found out that they use incorrect domain on their email address*
Also me: (╯°□°)╯︵ ┻━┻