docker-mail/pages/spf.md

title, Description

title	Description
SPF configuration	How to configure SPF for No Fuss Computings docker mail server.

Sender Policy Framework (SPF) is defined in RFC7208, Sender Policy Framework (SPF) for Authorizing Use of Domains in Email.

DNS SPF text record example:

IN    TXT    "v=spf1 mx a ip4:192.168.0.100 ip6:2001:ef3:2911::/64"
                 " a:mail.example.org a:mail2.example.org -all"

1. v=spf1 Version attribute. only v1 available.

2. mx a DNS record type. This indicated that mx and a records within the domain are authorized senders.

3. ip4:192.168.0.100 indicates that an ipv4 address as specified is authorized as a sender.

4. ip6:2001:ef3:2911::/64 Sepcifies that an ipv6 subnet is authorized as a sender

5. -all specifies a fail if the sender doesn't match what is specified in the record. other valid qualifiers are "+" pass, "-" fail, "~" softfail, "?" neutral

!!! tip To allow only specified MX DNS records to be the only specified senders, create a record as follows:

``` text
IN    TXT    "v=spf1 mx -all"
```

If your MX servers only receive mail, then this option is not suitable. you'll have to use the hostname of the receiving server.

``` text
IN    TXT    "v=spf1 a:mail.example.org -all"
```