The reason I added the address validation for mail from was because
otherwise we had no guarantee that we could send a bounce. Validation
stopped us from getting a bunch of invalid addresses we would then fail to
bounce back to.
The lack of handling for quoted addresses has been true since day one,
however, and properly handling them would have required validation up and
down the whole stack, and gets into some challenging questions especially
when it comes to the "user enters an address" box. Do we require the user
to enter addresses properly quoted? Do we attempt to allow the nearly
everything that RFC 3696 talks about? If we do that, then just about
anything
they enter would be allowed and most likely would be wrong. How do you
display a quoted address, de-quoted so it looks nice but not like any email
address users are experienced with, or quoted which looks ugly but looks
closer to "right" and can be copy & pasted into places that expect an email
address?
Maybe there was some happy medium, but it almost certainly would cause
user confusion. The longer we didn't support them, the less likely they
were actually in use... and the more the bit Ale quotes below comes to play.
Of course, the other part that's really ugly is that some gmail addresses
have multiple dots in a row, sorta, in the sense that gmail addresses
ignore dots and some people got really creative in their use of them, so
the code does handle that, but I don't recall the specifics, whether that
applies only to @gmail.com addresses or what.
Brandon
On Sat, May 4, 2024 at 4:43 AM Alessandro Vesely via mailop <
mailop@mailop.org> wrote:
> On Thu 02/May/2024 21:02:28 +0200 John Levine via mailop wrote:
> > While debugging something else, I've been trying to send messages to
> myself
> > from the address a...@m.jl.ly. RFC 5321 says two dots in a row need to
> be
> > quoted, and I have checked that my mail system does indeed put in the
> quotes
> > and it says
> >
> > MAIL FROM:<"a..b"@m.jl.ly>
>
>
> Useless to recall the famous sentence of RFC 5321, where it defines the
> address
> syntax (Section 4.1.2):
>
> While the above definition for Local-part is relatively permissive,
> for maximum interoperability, a host that expects to receive mail
> SHOULD avoid defining mailboxes where the Local-part requires (or
> uses) the Quoted-string form or where the Local-part is case-
> sensitive.
>
>
> Best
> Ale
> --
>
>
>
>
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