I recently switched a domain's email service to Google. The only records I changed in the name server was the MX records, pointing to Google. To my surprise, emails sent to and from Google Apps work just fine. So is there a point in changing the A, CNAME, and other records in the name server for a domain if the only use of the domain is email?
When you are sending a mail to
firstname.lastname@example.org,The mail server of
example.com is determined using
MX records. Assume the following records for example.
example.com MX mail.example.com mail.example.com A 188.8.131.52
MX record is found,
MTA will do a forward lookup for the name returned (here
mail.example.com which will return
184.108.40.206 )and try to deliver the mail to
220.127.116.11. If no
MX record is found for the domain and only the following DNS records exist
example.com A 18.104.22.168
MTAs will try to connect to
A record of the domain itself, (here
22.214.171.124) and try to deliver the mail. only when no
MX record exist for that domain.
A record will be used. Hope this clarifies why just changing
MX records worked for you.
MX records are used by and for mail servers so email can be exchanged.
Changing a domain to use Google Apps for email service only requires changing all the mail related DNS entries.
A and CNAME records are used to convert people friendly URL's into IP addresses.
If you have a CNAME record for mail.yourdomain.com, you are better off changing it too but if no one opens a page to that URL it might not matter.
A and CNAME records for any other part of the domain (web pages for example) should remain unchanged.