Failed to send emails that I never sent

Some months ago, I started to receive some emails from “Mail Delivery Subsystem” ( Despite this is “automatic” failure email, I thought these emails were spam, so I just ignored. But today much more emails, and this started to disturb me.

These emails are send from (there is a icon that indicates a reply email) and says that “ couldn’t be found”. “MYEMAIL” is the email that is receiving these messages, but with domain “” (I don’t have any email from this domain).

In these emails, there is always a attached file about something attractive, like diets and wines. I think the most curious detail is that I was receiving these emails but in a “normal way”. Before receiving from mailer-daemon, I was receiving like normal spam, even with the same subject, and at some point this has changed to mailer-daemon. Another detail is despite these emails always have a attached file, I can’t see the attached file icon’s until I open the email. Only then, when I close the email, I can see the attached file icon’s. Obviously I never downloaded these files

I already changed password, checked login’s entries and everything seems to be normal. I can just block emails from, but I’m concerned about why this is happening.