It is not unusual to get emails with the TO having an address that is not your own, this is usually where an email has been sent to a group of addresses using Bcc. These emails may be clever fakes.
I often get them and regard them as dangerous spam or spoofed/forged emails.
Any email that is not address to yourself is suspect, or sometimes it is to recipients
It is best not to click on any links or images and downloads/attachments in these types of emails.
Also, if you think you have been hacked, check that no auto forward has been set up in your email account by the hacker.
It is possible other sessions of an email can remain logged in, I recently had a message on logout to close all browsers which was unusual after finding messages in my trash sent from myself which I had not sent.
Virgin have removed the facility to close all sessions which may be less secure.
Password changes can be tricky, I have been locked out a few times myself. there is time delay changing passwords that can be approx 10 minutes
I suggest you do some antivirus scans also.
I no longer use my virgin ISP email and use "more secure" free email providers that have 2 factor authentication such as Outlook.com, Gmail.com, Yahoo.com.
