I created an online account and received the usual welcome email. In addition, however, an "Undelivered Mail Returned to Sender" email appeared in my inbox one second later. I am the supposed sender, and the website I registered on the recipient. The email which could not be delivered contains (in plain text as well as in a .csv attachment) all the information I had entered upon registration. The website itself seems trustworthy/legitimate.
Since I definitely did not send an email (and do not see an email in my outbox or sent folder), I wonder how this is possible and whether this poses a security risk.
I found a related question here on this site ( i-received-an-undelivered-mail-is-my-email-address-used-maliciously), but I can't quite connect the dots.
- It seems unlikely to me that my email was hacked or maliciously used at exactly that point of time. The password I used on the website was randomly generated and is almost surely unique among all my passwords.
- If the header was forged and someone was trying to deceive me that I had sent an email, I'd wonder why the email and attachments contained the information I entered upon account creation. If that was a third party, would this mean the website could be compromised? Again, the timing make me wonder if this is realistic.
- If it was a poorly configured foreign server, why would it appear as if I had tried to send an email with that specific content. The information, as far as I understand, should have been submitted/sent through the registration form. Why send another email with the same information? Why would it appear as if the email was sent from my email address?
I would appreciate if someone could shed some more light on this. Please find part of the email header (with my and the website's info anonymized) below. Please excuse the use of an image, but otherwise this post was classified as spam.
I also found failed-to-send-emails-that-i-never-sent, but the context is quite different to mine. In my case, the undeliverable email seems to be specifically related the the registration on the website.