Isn't this handled by ITS these days?

Likely... Are there discoverable docs which describe how anyone could find out somehow?

While there are still some special cases that forward mail to donate@ in files controlled by SRE these should all be about wikipedia.org (for example jimmy@wp),but not wikimedia.org.

Please see T297915 for context when donation-related aliases were moved from SRE to ITS.

This should be added on the Google side.

In T403986#11159496, @Aklapper wrote:

Likely... Are there discoverable docs which describe how anyone could find out somehow?

Not since we moved from exim to postfix afaict.

In T403986#11159409, @Reedy wrote:

Isn't this handled by ITS these days?

[Adding @jhathaway]

EDIT: Please refer to @Dzahn's comment instead.

We do handle some aliases (mostly the ones that were historically in place; T122144) but looking at profile/postfix/mx.yaml, donation@wikimedia.org is handled by ITS indeed. Adding Jesse for the final confirmation.

On the mx-in servers you can obtain routing information via sendmail -bv, however it is a bit more annoying to work with compared to exim -bt

at present donations@wikimedia.org does not exist:

<donations@wikimedia.org>: delivery via
    aspmx.l.google.com[2607:f8b0:4004:c08::1b]:25: host
    aspmx.l.google.com[2607:f8b0:4004:c08::1b] said: 550-5.1.1 The email
    account that you tried to reach does not exist. Please try 550-5.1.1
    double-checking the recipient's email address for typos or 550-5.1.1
    unnecessary spaces. For more information, go to 550 5.1.1
    https://support.google.com/mail/?p=NoSuchUser
    af79cd13be357-81b5e8a6f62si718185a.593 - gsmtp (in reply to RCPT TO
    command)

and donation@wikimedia.org is handled by gmail:

<donation@wikimedia.org>: delivery via aspmx.l.google.com[172.253.115.27]:25:
    250 2.1.5 OK 6a1803df08f44-720b803d8afsi64982156d6.914 - gsmtp

I agree with @Dzahn and @ssingh that it would be best to have ITS add this alias.

Thank you everyone - the history of this address is why I wanted to confirm, thank you for your help! We'd greatly appreciate if there's a discoverable way we can check this and/or documentation you can share with us, in the meantime I'll work on getting this updated in Google.
Thanks again,
Dustin

sendmail -bv

aha, thanks for adding that, @jhathaway

discoverable way we can check this

Not really, because that is in a non-public repo that requires shell access. But you can just assume if it's in the @wikimedia.org domain (not wikipedia.org, a subdomain or other domains) and an alias that a non-SRE team asks you about then it's extremely likely on your side.

All we have left on our side is SRE-internal, with one notable exception of benefactors.wikimedia.org.

In the relevant file on our side there is this comment:

76   ## PLEASE DO NOT ADD ANY NEW ALIASES HERE
77   ## UNLESS THEY ARE STRICTLY SRE-INTERNAL!
78   ##
79   ## EVERYTHING ELSE SHOULD BE DONE IN GOOGLE BY ITS.
80   ## mail techsupport@wikimedia.org to send requests to ITS

Maybe default to searching for it in the Google admin console.

Another way to look for history is to browse the title of the subtasks of T122144.