@GDL2
Then I think I should help again. Be prepared for a bit of a read.
There are two types of compromise which can happen to email accounts. The first is spoofing. The account is not interfered with. But what happens is that some uses your email address to disguise themselves when they spam. It can't be stopped. You have to live with it till it passes. What you see on your computer/device is a bunch of non-delivery messages from ISPs where the spoofer has sent emails but the recipients don't exist. VM have a useful and non-tech article here:
https://community.virginmedia.com/t5/Email/Email-Spoofing/m-p/2941294#M102560
Hacking is much more serious. This where the hackers get hold of not only your email address (virtually any one can do this, you spread it all over when you send mail or register on web sites so who doesn't know it, but then again how people know your physical home address - thousands?) but they also get your password. Now that is serious. The information often comes from data stolen from sites which themselves have been hacked. You can check this by Googling for "I've been pawned" and checking your email address. People often use the same credentials for their email accounts as they use for web sites, say when shopping. Sometimes the hackers guess because people use very common passwords.
But what the hackers then have is complete access to your email credentials, address and password, and without you being aware of it send email using those credentials via VM 's own mail servers but not using VM as an ISP. You can't see this but VM can. They take action to stop it because otherwise their mail servers will get blacklisted and many, many others will be stopped from sending legitimate mail. The hackers can also interfere and hijack your on-line accounts with Amazon and Spotify etc. by pretending to be you.
There's actually a lot more to it than this. I've skimmed over the topic but you should have enough to be getting on with.
Hope that helps.
Just one final tip on email security. Follow VM's guidance here for creating a secure password and never use the same password elsewhere that you have chosen for email.
https://www.virginmedia.com/help/how-to-create-a-strong-password
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