I'll try to rephrase it then: I have a mail address I can redirect to whatever mail I choose, let's say is is called firstname.lastname@example.org, and I am trying to redirect it to my Disroot mail address. Also I do not own the address domain, which is example.org here.
The problem was that when I tried to send a mail to email@example.com, I get this SPF fail message. answer.
So I made a few tests and it appears I get this answer only when I send a mail to firstname.lastname@example.org from a Microsoft e-mail address.
Correct me if I'm wrong, but I guess the disroot.org mail server sends back this answer in every cases because I do not own the example.org domain, and some mail services choose to send anyway the mail, but Microsoft doesn't allow it.
Is there anything I can do to change this behavior?