DKIM - CNAME or TXT?
A DNS record for DKIM can be entered either as a CNAME record or as a TXT record. The type to be used depends on whether the DNS record contains a key or a pointer to a key. The following applies:
The Amazon SES email server, which is covered in the main article, uses pointers to keys and therefore the CNAME type is used for the DNS records, as you can see in the Amazon SES documentation.
An email server that does not use the CNAME type but TXT is the Google Gmail / G Suite email server. It provides a key directly and thus the DNS record to be entered must be of the TXT type.
The type of DNS record for DKIM affects how data is to be entered
The type of DNS record affects how data is to be entered. If the type is CNAME, data is entered according to this principle:
If the type is TXT, data is entered according to this principle:
Exactly what the data content should be is determined by the email server. But you do not need to delve into this too much, you just copy the content from the email server's control panel to the website's control panel. Just make sure that all data is copied and nothing is missing.
More information about CNAME, TXT and DNS records for DKIM can be found on this web page:
What is a DKIM record?
More general information about DNS records, CNAME and TXT can be found on the following web pages:
DNS records (NS, A, MX, CNAME, SPF) explained
Google - DNS Basics
More articles are available from the article index page.