[docsaintly]

I think using example.com is a bit of a trick question. It is known as an example domain which is invalid for all purposes, except of course for serving as an example. :)

https://www.iana.org/help/example-domains

[olddustytrail]

Exactly. Not valid because it can't be routed.

[paulnpace]

An explanation of the use of example.com would have informed users that addresses should be evaluated as such, otherwise, AFAICT, all of the examples provided are invalid.

[TMWNN]

Yes. If I'd known that other questions would also use example.com, I would have answered the first question correctly.

[wredcoll]

I've actually been wondering for a while if example.com is a valid example email address.

[mdaniel]

Well, "valid," yes, but "deliverable" thankfully, no

  $ dig MX example.com.

  ;; ANSWER SECTION:
  example.com.  3600 IN MX 0 .

Almost certainly the same for its .org .net and .example friends. There were some other TLDs that were designed for use in documentation, but I don't have the RFC in front of me right now to cite them

[SoftTalker]

Some of the other examples which are "technically valid but obsolete" I would consider safe to call invalid for practical purposes.

[samwho]

Yeah, I almost put a disclaimer at the end saying that while these examples are valid according to the spec, that has no bearing on whether they’re usable in practice. Email is the Wild West.