WIP: `FormatOptions`: Feature `ConvertPunycodeToIdn`

[NicolaiSoeborg]

Is your feature request related to a problem? Please describe. A lot of places requires working with punycoded mails as the IDN form is not handled correctly. But when parsing, mails are turned into IDN form, i.e. MimeKit.MailboxAddress.Parse("X@xn--sb-lka.org").Address == "X@søb.org"

Describe the solution you'd like It would be nice with an option to keep the address in punycoded form.

Describe alternatives you've considered I guess users of this library can also do something like:

if (mailbox.IsInternational)
    mail = mailbox.LocalPart + "@" + MailboxAddress.IdnMapping.Encode(mailbox.Domain)

Additional context This is a suggestion for adding that. Comments are welcome!

[jstedfast]

FormatOptions.International is more-or-less meant for this already.

I guess users of this library can also do something like:

if (mailbox.IsInternational)
    mail = mailbox.LocalPart + "@" + MailboxAddress.IdnMapping.Encode(mailbox.Domain)

Alternatively, you can do this instead:

var email = MailboxAddress.EncodeAddrspec (mailbox.Address);

That said, perhaps the parser shouldn't decode International Domain Names and/or perhaps a InternationalAddress property could be added and Address could enforce a punycode encoded address?

The only issue with that is it would break existing expectations, so perhaps a better approach would be to add LegacyAddress or SafeAddress or something (not sure I like either property name, but you get the idea).

Before I jump out of the starting gate, though, what scenarios do you need supported, exactly?

• [ ] In other words, do you need to enforce punycode encoding for mailbox addresses when writing the MimeMessage back out to a stream (e.g. to disk or when sending the MimeMessage via SMTP)?
• [ ] Do you need this to happen even if/when FormatOptions.International is set to true?
• [ ] Is it necessary for MailboxAddress.Address (or a replacement property) to be punycode encoded for convenience?
• [ ] Do you need mailbox.ToString(FormatOptions) to output the punycode encoded address?
• [ ] Other scenarios that I've missed.

Sounds like you want option 3, but what about the others?

Alternatively, is MailboxAddress.EncodeAddrspec (mailbox.Address) enough now that you know about that option?

[jstedfast]

BTW, if you only ever want punycode-encoded domains, another option is to swap out the MailboxAddress.IdnMapping implementation to one that doesn't encode/decode (or one that always converts into the encoded version).

You just need to implement the IPunycode interface: https://mimekit.net/docs/html/T_MimeKit_Encodings_IPunycode.htm

[jstedfast]

I'm going to close this because I haven't heard any response, but if there is still interest in this we can reopen and have more discussion on how best to meet your needs.