Situation: I am sending emails from
firstname.lastname@example.org. My DNS for
mydomain.com is correctly configured with an SPF record. The recipient at
example.org is able to receive my emails just fine (it says "SPF: pass" in the headers).
Now, Alice configures
email@example.com to redirect any email to
firstname.lastname@example.org no longer has a mailbox or account attached to it, it's simply a forwarding address to
I send an email to
email@example.com again. However, the receiving end at
otherdomain.com now thinks the email is coming from
example.org (as that's the last forwarding server or IP address), which of course does not have the SPF record that I have on
mydomain.com. So it now marks my emails as failed for the SPF check, and puts in the spam folder.
So in short, the problem is: Due to redirecting email (on which I have no influence) the final recipient erratically thinks my email fails the SPF check, and discards it as spam. Is there a way to avoid this?
Also, I noticed sometimes that if I don't have a DKIM record (and not using DKIM) but the forwarding server does, then the recipient thinks my message failed the DKIM check as well. Whereas I don't even use DKIM, nor do I have a DNS record for this. It's the forwarding server (
example.org in this example) that makes the recipient think the email should be DKIM signed.
(edit) Note that if I email to
firstname.lastname@example.org directly, the problem does not occur. My email is then considered to be valid (it passes the SPF check) and does not get filtered as spam. However I can't know in advance if someone is using a forwarding address.