In Site Administration > Authentication > Domains section -- I have added a domain and verified it (@example.com).
We also have some users who use email addresses with sub-domain like this (@tw.example.com). Question is I can add this sub-domain in the Domains section, however I am never able to verify it. I am using DNS method for both the verifications. I do see that the TXT string is the same in both cases.
A followup question will be if sub-domain is not necessary to add explicitly, then would "Reset passwords now" button trigger a password reset for users which have email address from sub-domain