'Bad username' refers to the user id that is between ! and @ in your address (i.e. nick!user@host). It must comply with some specific rules:


* In a mixed-case name, if first char is upper, one more upper may appear anywhere.
* A mixed-case name must have an upper first char, and may have one other upper.
* A third upper may appear if all 3 appear at the beginning of the name, separated only by "others" (-/_/.).
* A single group of digits is allowed anywhere.
* Two groups of digits are allowed if at least one of the groups is at the beginning or the end.
* Only one '-', '_', or '.' is allowed (or two, if not consecutive), but not as the first or last char.
* No other special characters are allowed.
* Name must contain at least one letter.



mIRC users may change their User ID in the following way:

Options > Email
Options > connect > Identd.