Understanding SPF, DKIM, and DMARC for Email Delivery

Without a proper SPF or DKIM setup, your emails reliably end up in spam or get rejected. 'p=none' is just a way of saying 'I’m not really enforcing policies,' which does leave the door open for spoofing. Incoming DMARC checks depend heavily on the receiving server. You can't disable them unless you control that server directly.

Two things I always make sure to set are SPF to hard fail and DKIM to reject. It prevents a lot of spoofing.

From my experience, there's a lot to consider, and the only real way to know if one domain can get emails from another is to test it. SPF, DKIM, and DMARC are clear-cut, but the spam filters will drive you up the wall when trying to determine why a specific email lands in junk.

1. Emails can be delivered, but they often land in spam or junk folders. Occasionally, they might reach the inbox if the sender’s reputation is stellar, though that's rare.

2. Yes, 'p=none' basically means just monitoring – spoofed emails can still go out, but they often get flagged as suspicious.

3. No, you don’t have control over DMARC checks. Providers look at the sender's reputation, authentication results, and user signals.

1. It really depends on the receiving server's spam filter settings. Some might mark emails lacking SPF, DKIM, or DMARC as spam, but there’s no technical blockade that stops delivery entirely.

2. DMARC and SPF serve different functions. DMARC relies on SPF and DKIM to set its actions. Even if a sender has a hard fail on their SPF, the receiving server will likely just raise the spam score instead of outright blocking the email. DKIM adds a digital signature validating the sender's domain, and DMARC directs actions based on SPF and DKIM results.

3. When an email arrives, the receiving server checks the sender's domain policy for SPF and DMARC. If both SPF and DKIM fail and DMARC is set to 'NONE', the message can still arrive but will usually land in spam. If DMARC is set to 'QUARANTINE' or 'REJECT', then it’s a different story – QUARANTINE goes to junk, and REJECT doesn’t deliver the mail at all.