By enabling SPF, you ensure that spam through your domain is rejected. If a spammer attempts to send mail from an address in a domain that doesn't have an SPF record, your recipient's email server will reject the message. 

Creating an SPF record for Proton Mail

Here are the steps to set up SPF for Proton Mail :

• Login to your DNS management console 
• Navigate to Tools & Settings > DNS Template
• You need to edit the DNS TXT record related to SPF
• An SPF TXT record for Proton Mail will have the following syntax: 

mydomain.com    TXT  v=spf1 include:_spf.protonmail.ch -all

• Publish this record in your DNS records section for your respective domain. 

Note: If you don’t have an SPF record previously for your domain, simply publish the above-mentioned record to enable SPF for outgoing emails using Proton Mail. If you do have an existing SPF record in your DNS, you need to modify it to include Proton Mail, as shown below:

Previous SPF record:  v=spf1 include:spf.domain.com -all

Modified SPF record:  v=spf1 include:spf.domain.com include:_spf.protonmail.ch -all

• Save changes 
• Wait for 72 hours to allow your DNS to process the changes 

Finally, you can look up your record using our SPF record lookup tool, and enable DMARC for your domains: take a DMARC trial.