To ensure that your emails are sent correctly and are less likely to be labelled as spam, add a record to your SPF that contains the list of email addresses provided to Marketo in this welcome email.
Sign in to your DNS management console
Go to Tools & Settings > DNS Template
You need to edit the DNS TXT record related to SPF
An SPF TXT record for Marketo will have the following syntax:
yourdomain.com TXT v=spf1 include:mktomail.com -all
Publish this record in your DNS records section for your respective domain.
Note: If you don’t have an existing SPF record for your domain, simply publish the above-mentioned record to enable SPF for outgoing emails using Marketo. If you do have an existing SPF record in your DNS, you need to modify it to include Marketo, as shown below:
Previous SPF record: v=spf1 include:spf.zoho.com -all
Modified SPF record: v=spf1 include:spf.zoho.com include:mktomail.com -all
Save changes
It will take 24-48 hours for your DNS to process the changes