Synonyms VS Email accounts Synonyms are domain masks used to map or alias DNS names to a specific email domain. Synonyms are not real email addreses. Synonyms are a way to map email addreses to a specific domain. for example:

• DOMAIN-A.com
• SYNONYM-A.com mapped to DOMAIN-A.com

user@DOMAIN-A.com is a real email address, while user@synonym-A.com is just an alias that maps through DNS to user@DOMAIN-A.com because in DNS MX record settings all point to the same IP address of the real domain, in this case DOMAIN-A.com.

There is no physical email account at user@synonym-A.com only at user@DOMAIN-A.com.

If user@DOMAIN-A.com and user@SYNONYM-A.com are both recipients in the same email header, then only the mail addressed to user@DOMAIN-A.com will get delivered.