This source is known to forward email
FastMail is capable of sending DMARC compliant email because they support custom SPF and DKIM configurations that achieve DMARC alignment. FastMail is a Corporate Email Platform and is often used by Network and Email Administrators teams.
The link just below is a resource on how to configure this source to send DKIM-aligned email on your behalf. You will complete this configuration by (1) following the source's instructions and (2) adding the required entries into your DNS. https://www.fastmail.help/hc/en-us/articles/360060591153. Search for the section titled 'DKIM'.
The link just below is a resource on how to configure this source to send SPF-aligned email on your behalf. You will complete this configuration by (1) following the source's instructions and (2) adding the required entries into your DNS. https://fastmail.blog/advanced/spf-dkim-dmarc/ Search for the section titled 'SPF'.