Mail Forwarding (Self-Host)

DNS Configuration

How to correctly configure DNS for domains and subdomains that will use the mail forwarding service. Includes PTR, MX, SPF, DMARC, and database authorization.

This guide explains how to correctly configure DNS for domains or subdomains that will use the Mail Forwarding Service, so they can be:

Accepted by Postfix
Authorized in the database (domain table)
Used by the API and UI

DNS must be configured before inserting the domain into the database. If DNS is wrong, mail delivery, forwarding, SPF, or DMARC will fail.

Step 1 — PTR / Reverse DNS (mandatory)

PTR (reverse DNS) must be configured first, directly at your VPS or hosting provider.

Generic model

IPv4  ->  mail.your-domain.tld
IPv6  ->  mail.your-domain.tld

mail.your-domain.tld  ->  IPv4
mail.your-domain.tld  ->  IPv6

Real example (current setup)

PTR: 161.97.146.91              -> mail.abin.lat
PTR: 2a02:c207:2298:1997::1     -> mail.abin.lat

mail.abin.lat -> 161.97.146.91
mail.abin.lat -> 2a02:c207:2298:1997::1

PTR is not configured in Cloudflare or normal DNS panels. It must be set at your VPS/hosting provider. PTR must match the hostname used by Postfix (myhostname). Missing or mismatched PTR is the #1 reason for outbound mail rejection.

Step 2 — DNS records for a domain

Example domain: example.com Mail host: mail.abin.lat

Required records

Type	Name	Content	Priority
MX	@	mail.abin.lat	10

SPF (recommended)

example.com TXT "v=spf1 ip4:<YOUR_IPV4> ip6:<YOUR_IPV6> -all"

Example:

example.com TXT "v=spf1 ip4:161.97.146.91 ip6:2a02:c207:2298:1997::1 -all"

DMARC (recommended)

_dmarc.example.com TXT "v=DMARC1; p=none; rua=mailto:dmarc@example.com; fo=1"

Step 3 — DNS records for a subdomain

Example subdomain: sub.example.com Mail host: mail.abin.lat

Required records

Type	Name	Content	Priority
MX	sub	mail.abin.lat	10

SPF

sub.example.com TXT "v=spf1 ip4:<YOUR_IPV4> ip6:<YOUR_IPV6> -all"

DMARC

_dmarc.sub.example.com TXT "v=DMARC1; p=none"

Step 4 — Authorize the domain in the database

After DNS is fully propagated, insert the domain (or subdomain) into the domain table:

INSERT INTO domain (name, active) VALUES ('example.com', 1);

For subdomains:

INSERT INTO domain (name, active) VALUES ('sub.example.com', 1);

Once inserted:

Postfix will accept mail for the domain
The API can create aliases
The UI can expose the domain

Common Mistakes

Mistake	Impact
PTR missing or wrong	Outbound mail rejected
MX pointing to wrong host	Mail never reaches your server
SPF not matching server IP	Forwarded mail may fail DMARC
Domain added to DB before DNS	Mail will fail even if alias exists
Using hostname without A/AAAA	Postfix cannot identify itself correctly

Summary Checklist

Before adding a domain to the database:

PTR → mail.your-domain.tld
mail.your-domain.tld → A / AAAA records
MX → mail.your-domain.tld
SPF includes server IP(s)
DMARC present (at least p=none)
Domain inserted into domain table

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