Forgive me if this is the wrong place to post or if this issue is already known; I just wanted to provide a small bit of feedback as a new member.
It looks like these emails are sent out via Amazon’s SES SMTP service, yet the SPF record for hacman.org.uk only specifies Gmail as an allowed sender, and alerts.hacman.org.uk has no SPF record at all.
Setting the SPF record for [alerts.]hacman.org.uk to the following should fix this:
v=spf1 include:_spf.google.com include:amazonses.com ~all
Whoever manages the DNS with Cloudflare would need to make the change assuming this seems reasonable. Again apologies if this is the wrong place, not inducted yet so thought I’d dump it here before I forgot!