Strange iCloud email address?

Hello everyone,

For some time now, I have had the feeling that someone is accessing my Apple ID, as I keep finding strange files on my devices that I can't open, or strange emails/messages with my old mobile number or from a sender with my previous surname… I suspect that someone is trying to sabotage me, and I'm guessing it's my ex-husband.

My Apple ID is normally “myname1234@icloud.com”

I recently received an email containing my iCloud email address. The sender was: "myname1234_at_icloud_com_n4k711bp9cfdr2_915f6334@icloud.com"

What does this mean? I can't find these letter/number combinations anywhere on any of my devices, and I'm not getting anywhere with my research online. Can someone explain to me what this could mean?

Many thanks and kind regards

(Note: My iCloud email address is of course not really “myname1234” but my real name with the year.)