I Uncovered A Serious Gmail Security Bug
jdosstech.postach.io
jdosstech.postach.io
milesstandish@gmail.com and miles.standish@gmail.com are the same account.
To prove this, log out of the former, and into the latter using the same password. You will see all the same emails. Sign out and in again with m.i.l.e.s.s.t.a.n.d.i.s.h, using the same password.
Those emails you are receiving in error are probably for someone like miles.p.standish, who forgot his middle initial when sharing his address.
Sending email to miles.s.t.andish+123@gmail.com will still deliver email to milesstandish@gmail.com.
This is very helpful if you want to make multiple accounts on any website without going through the trouble of making multiple email addresses. Particularly helpful if you have multiple test accounts in your web application.
https://support.google.com/mail/answer/10313?hl=en
This has been there since launch, afaik.
Click on "Your address is similar but has more or fewer dots (.) or different capitalization." to expand the explanation.
We had to add a link to this support document to the security@google.com autoresponder because people misunderstand this behaviour so often (They think they're getting someone elses mail, but someone just sent it to the wrong address).
E.g.: if you create abcdef@gmail.com, then a.bcdef@gmail.com , ab.cdef@gmail.com and so on become unavailable and are directed to your main account.
Once someone has created j.smith@gmail, jsmith@gmail can no longer be created -- because they are the same account. It's not possible for you to have j.smith@gmail and someone else to have jsmith@gmail.
I get other peoples' mail all the time. It's not because gmail is misdelivering mail with dots in account names. It's because someone has another letter in their account that somebody left out (jjsmith, jpsmith, jsmith1, etc.) It's the sender, not gmail, who is directing the mail to the wrong inbox.
If that is not what you mean, you should edit it to make it clearer.
You can log in to that other account yourself, with your own password. You'll find that you have logged into your own account rather than anyone else's.