fix(mail): prevent whitespace in domain part of addr-spec

Updated the addrParser's consumeAddrSpec function to clarify that whitespace characters are not allowed in the domain part of an email address. Removed the call to skipSpace to enforce this rule.

Author: noahchiu22

src/net/mail/message.go

@@ -549,7 +549,8 @@ func (p *addrParser) consumeAddrSpec() (spec string, err error) {
 
 	// domain = dot-atom / domain-literal
 	var domain string
-	p.skipSpace()
+	// domain part does not allow whitespace characters, so skipSpace cannot be called here
+	// p.skipSpace()
 	if p.empty() {
 		return "", errors.New("mail: no domain in addr-spec")
 	}