DNS records serve as listed street addres and phone number of your mail server. People on Internet can find you from yellow page.
A. The following DNS records are responsible to address your mail server with:
1. A record, resolving domain name to your static server IP address (MUST)
2. MX record, keeping track your mail server's hostname followed by your domain name (MUST)
3. TXT record, holding SPF values for antispam purposes (PLUS)
4. SRV record, providing information for SMTP, POP3 and IMAP protocol auto detection services (OPTIONAL)
B. Once records are defined, make sure name server (NS) records on your domain name registration service provider point to name server hosts given by your DNS hosting service provider unless both Internet and DNS hosting service providers are the same.
C. Last step, we test if all the settings are working with the following tools:
1. both tools on MXToolBox website and nslookup command
2. EVO's 'Network setting status' on status page: