When it comes to email address normalization, it sounds like we could do with a standardized way for a domain to express normalization policies. Could be as si

When it comes to email address normalization, it sounds like we could do with a standardized way for a domain to express normalization policies. Could be as simple as publishing a set of regular expression subsitution rules, specifying (for example): * render to lower case (because this particular domain is case insensitive) * drop periods (because this domain treats them like gmail does) * drop '+' and any subsequent characters (because this domain treats them like gmail does) * ASCII only (because mail software is old, and doesn't support unicode) Etc. Each domain could then publish their own rule, perhaps in a DNS txt record, and anyone needing to check if two email addresses alias to the same could run the correct checks.