I have this regular expression for valid email addresses which works well: ^(?=[\w\s])\s*[- .'\w] @[-.\w] \.[-.\w]{2,}\s*$

However, users are sometimes entering an address like "[email protected]". I could exclude "co" from my regex, but I still want to allow "[email protected]", see here.

I looked at this post but I don't know how to include that in the part [-.\w]{2,} of my current expression.

How can I alter my regular expression to disallow ".co" at the end of an email address?

CodePudding user response：

You could write the pattern without the lookahead at the start as:

^\s*[- .'\w] @\w (?:[-.]\w )*\.(?!co\s*$)[a-z]{2,}\s*$

Note that [- .'\w] and \w limits the range of valid email addresses.

The pattern matches:

• ^ Start of string
• \s*[- .'\w] @ Match optional whitespace chars and repeat any listed chars in the character class until matching @
• \w (?:[-.]\w )* After the @ start with matching 1 word chars and optionally repeat either . or - and 1 word chars
• \.(?!co\s*$) Match a dot and use a negative lookahead asserting not co and optional whitespace chars until the end of strinng
• [a-z]{2,}\s* Match 2 or more chars a-z and optional whitespace chars
• $ End of string

See a Regex demo

If you don't want to allow matching leading whitespace chars, you can omit \s* from the start and the end of the pattern.