Why not just send an email to every website?

I could probably try to automate that, but to what email address? I’d have to hit a selection of common ones, info@, support@, abuse@, maybe others?

I’d use “webmaster@”, which is a pretty long-running convention, though I don’t know how many people have it set up. I don’t know if there’s an RFC backing that.

If you’re going to provide a standard contact admin email for a website, that’s where I’d expect it to be, at any rate.

EDIT:

Yeah, webmaster@; RFC 2142.

https://www.rfc-editor.org/info/rfc2142/

RFC 2142: Mailbox Names for Common Services, Roles and Functions

Various Internet documents have specified mailbox names to be used
when reaching the operators of the new service; for example, [RFC822
6.3, C.6] requires the presence of a <POSTMASTER@domain> mailbox name
on all hosts that have an SMTP server.  Other protocols have defacto
standards for well known mailbox names, such as <USENET@domain> for
NNTP (see [RFC977]), and <WEBMASTER@domain> for HTTP (see [HTTP]).
Defacto standards also exist for well known mailbox names which have
nothing to do with a particular protocol, e.g., <ABUSE@domain> and
<TROUBLE@domain>.

The purpose of this memo is to aggregate and specify the basic set of
mailbox names which organizations need to support.

5.  SUPPORT MAILBOX NAMES FOR SPECIFIC INTERNET SERVICES

For major Internet protocol services, there is a mailbox defined for
receiving queries and reports.  (Synonyms are included, here, due to
their extensive installed base.)

MAILBOX        SERVICE             SPECIFICATIONS
-----------    ----------------    ---------------------------
POSTMASTER     SMTP                [RFC821], [RFC822]
HOSTMASTER     DNS                 [RFC1033-RFC1035]
USENET         NNTP                [RFC977]
NEWS           NNTP                Synonym for USENET
WEBMASTER      HTTP                [RFC 2068]
WWW            HTTP                Synonym for WEBMASTER
UUCP           UUCP                [RFC976]
FTP            FTP                 [RFC959]