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MX records are DNS records that tell email systems how to route email for a given domain. When a sending server needs to deliver an email, it will look up the MX record of any/all of the recipients. Public DNS will return an IP address or A record of the destination server. The sending server will then attempt a connection to the returned IP address.
Things an MX record does: Tell a sending server how to deliver mail for a given domain
Things an MX record does not do: Limit email connections for a given domain to a specific IP address or FQDN
Affect your outbound mail in any way.
FAQ: Is there a way to only route certain email addresses in my domain to a specific server and some to other servers? No. MX records are an all-or-nothing deal. Any subsequent splitting of traffic would have to be done after the MX delivery
Do my org's MX records have anything to do with our outbound traffic? No, unless you have an MX entry in your SPF record (which is typically not recommended)
I've heard changing our MX record will result in lost email for 5-30 minutes, is this true? In most cases, no; as long as you test the connection to the destination from the new (changed) MX record, you will not lose any messages.
