Spammers and misspellings
This isn’t something ordinary users will see much of. But come again if you’re the administrator of a busy mailserver…
Spammer lists of e-mail addresses are full of misspellings. I can only imagine where they’re coming from!
*improper line breaks? lastname-firstname.lastname@domain.tld is quite common
*an extra or missing first letter. Yep, they lose the first character of the username, or even append one or more.
*Made up usernames. Sure, that’s a given, they do dictionary attacks, after all.