I've got 2 Gmail accounts I'm logged in at the same browser - a personal one and a work one. So these are 2 different accounts and I have to switch between them in order to see appropriate emails.
But few minutes ago I've mentioned in my work account an email intended to arrive into my personal account!
What does make me think it's a Gmail fault but not something else?
1. Technical headers of the emails show no link with my work account. The headers are saying it was intended and delivered to my personal account.
2. There's no active forwarding or mail fetching rules that might result in this on both personal and work accounts.
3. I'm seeing more that one erroneously delivered email.
4. Those problematic emails are available from different devices.
As a result it makes me think there was a bug in Gmail, and it lasted at least for a few hours.
P.S. I've seen the same failure again on 15/Oct. So probably the problem lasts.