13/21 here. Mostly got hung up on several "this was valid in earlier RFC, and later removed" kind of situations. There are several where I picked the correct answer, but where I know many websites that won't accept it as valid, and that's not even the more esoteric ones.

[–] NaibofTabr@infosec.pub 37 points 1 week ago (2 children)

Yeah I feel like the correct answer for anything obsoleted by a more recent RFC should be "Invalid".

[–] errer@lemmy.world 45 points 1 week ago

Complaints about the quiz? Send them to 💩@💩

[–] JohnEdwa@sopuli.xyz 25 points 1 week ago* (last edited 1 week ago) (2 children)

But they will work, and according to the spec, you have to build your system so that it can handle those cases. Obsolete doesn't mean incorrect or invalid, just a "you shouldn't do this any more".

Obsolete Syntax
Earlier versions of this standard allowed for different (usually more liberal) syntax than is allowed in this version. Also, there have been syntactic elements used in messages on the Internet whose interpretation have never been documented. Though some of these syntactic forms MUST NOT be generated according to the grammar in section 3, they MUST be accepted and parsed by a conformant receiver.

https://datatracker.ietf.org/doc/html/rfc2822#section-4

[–] frezik@lemmy.blahaj.zone 11 points 1 week ago

Some of those "obsolete" things are outright blocked for specific reasons. For example, routing addresses through multiple servers. It was abused by spammers, so it's almost always denied these days.

Looks like this:

<@foo.example.com@bar.example.com:123@example.com>

[–] NaibofTabr@infosec.pub 6 points 1 week ago

Well shit, yeah, that "MUST be accepted and parsed" is pretty explicit. That sucks. What is even the point of revising standards? How the fuck do we ever get rid of some of these bad ideas?