Network preparation - SomethingWithHorizons/mailserver GitHub Wiki

DNS

Set-up the following DNS records at your domain registrar to define the required DNS reference alias mappings, from (sub)domains to specific ip-address or relative to each other:

Host	Type	Content
@	MX	10 @
@	A	<public IP address>
imap	CNAME	@
smtp	CNAME	@
webmail	CNAME	@

@ domain root (e.g. example.org) being the alias MX source, referring - with priority 10 - to @ (i.e. the specific 'A' record) as its target. I.e. incomming e-mails go to -> @ ('A' record; in-turn referring to an IP).

@ domain root (e.g. example.org) being the alias A source, referring to <public IP address> (the external ip-address of the mailserver as the target) as its target. I.e. example.org -> 123.234.123.12

imap/smtp/webmail subdomains (i.e. webmail.example.org, etc.) being alias sources, referring to @ (i.e. the specific 'A' record) as its target. E.g. imap.example.org -> ('A' record; in-turn referring to an IP).

Firewall

Make sure the following TCP ports are open/forwarded to your servers:

To: Mailserver

• TCP/25 (SMTP - server to server)
• TCP/587 (SMTP - client to server)
• TCP/993 (IMAP - client to server)
• TCP/4190 (MANAGESIEVE - client to server)

To: Proxyserver

• TCP/80 (HTTP - client to server)
• TCP/443 (HTTPS - client to server)