SPF, DKIM, DMARC and BIMI explained

Four DNS records help decide whether your mail arrives. Here is what they do, what they look like and where things go wrong in practice.

• SPFSPF lists the servers that may send mail for your domain. It is a single TXT record in DNS, and it is broken surprisingly often.
• DKIMDKIM digitally signs every outgoing message. Receivers can tell whether it was changed in transit and which domain vouches for it.
• DMARCDMARC ties SPF and DKIM to the sender address your recipients actually see. It also tells other servers what to do with forgeries.
• BIMIWith BIMI, mailbox providers such as Gmail, Apple Mail and Yahoo show your company logo next to your messages. Before that happens, SPF, DKIM and DMARC have to be set up properly.