Sent emails have random sender email address

Question

A family member of mine is responding to my emails from different email addresses which are not hers.

e.g. I sent an email from "[e-mail]" to "[e-mail]". I received two responses from her, one from "[e-mail]", which contains no text, and one from "[e-mail]". This email contains the message she wrote.

Till now this happened twice, with two different unkownresponding email addresses.

My grandma is not using different email adresses on purpose. She uses a pc with Windows7 and Outlook. What is a common way to investigate this problem? At which points could the email address be changed?

Answer 1

If the provider is not Outlook Mail itself, the sending protocol is most probably SMTP. In SMTP, the sender can pretend to be someone else by changing the "From" headers in the email. The same concept is involved in phishing, where people send emails from a server and pretend to be someone they aren't. Technically I can send you an email and I can change the sender address you will see to anything I wish.

Outlook of course doesn't allow this. There has to be a misconfiguration. If you got two emails, both emails were in fact sent from the sender from two different addresses, and there's no doubt regarding that.

In Outlook, in the compose window, you can change the sending account by a simple dropdown named "From" above the "To" field.

Both accounts must be configured in order to send the email from it. It doesn't matter which address you sent the mail to. Your grandma can reply from whichever configured account she prefers. You need to check the accounts configured in her Outlook and remove the one she doesn't own.