Fastmail

Fastmail is capable of sending SPF-aligned emails, meaning that they use your domain name in the Envelope From (or Return-Path) of email messages.

This makes it possible to achieve DMARC compliance via SPF.

To allow Fastmail servers to send emails from your domain, create the following TXT record:

v=spf1 include:_spf.fastmail.com ~all

If you use the nameservers hosted by Fastmail, they will automatically create the following record:

v=spf1 include:_spf.fastmail.com ?all

It is recommended to change ?all to ~all, otherwise no SPF policy is applied.

Source • Learn more about ~all

Fastmail supports custom DKIM signatures domains. This makes it possible to achieve DMARC compliance via DKIM.

To set up Fastmail DKIM on your domain, add the following three CNAME records, replacing example.com with your domain name:

Source

Fastmail supports DMARC compliance via both SPF and DKIM, even with strict alignment.

Set up DMARC to:

• Receive email delivery reports to identify and fix authentication issues and find out who’s sending from your domain.
• Choose the action to apply when both SPF and DKIM are not aligned with your sender domain, blocking abuse attempts.

Use a DMARC monitoring tool like DMARCwise to simplify compliance and detect issues before they affect your domain reputation.

Here’s an example of a DMARC record, to be created as a TXT record on _dmarc.example.com:

v=DMARC1; p=none; rua=mailto:;

Fastmail allows setting strict alignment on both SPF and DKIM, so you may later strengthen the policy and change the alignment mode:

v=DMARC1; p=reject; rua=mailto:; aspf=s; adkim=s;

Guide to DMARC compliance