E-mail Address canonicalization

Domain part (the part after the @):

Todo

We need to choose a canonicalization form for the domain side of the e-mail address. There are risks for user presentation around phishing with IDNs, which we should be careful about.

Local part (the part before the @):

SMTP specs say this part is domain-specific, and byte-for-byte arbitrarily sensitive. In practice, nearly every e-mail domain treats the local part of the address as a case-insensitive string. That is, while it is permitted by the standards, John@example.org is very unlikely to deliver to a different mailbox than john@example.org. Autocrypt-aware MUAs will canonicalize the local part of an e-mail address by making it all lower-case.

Todo

some people (and some e-mail domains) have known variations which all deliver to the same account. For example, the mailbox that receives john@example.org might automatically receive all mail addressed like john-whatever@example.org. gmail today supports arbitrary dot injection (e.g. johndoe@example.org delivers to the same mailbox as john.doe@example.org). Do we want to try to support these somehow? It would be simplest to declare anyone using aliasing schemes like this as out-of-scope for Autocryptv1.

Todo

do we want to allow sophisticated users to explicitly merge known shared aliases as long as the domain side stays the same? For example, if i happen to know that jdoe@example.org delivers to the same mailbox as john@example.org, can i declare that to an Autocrypt-aware MUA? How would such an explicit merge affect state management?