Amigans.net notification emails marked as spam (due to SPF failure)

Since at least the 30th May, I've noticed that "[The Amigans website] Forums auto-notify : New post in thread" emails are going into my GMail's Spam folder.

The fault appears to be at Amigans.net's end (or more specifically the groupmail.com service it uses), as GMail reports:
Quote:

It appears the SPF record needs updating.

Just a note that this is still happening, even though it should be easy for the owner of "groupmail.com" to fix:

I'm not sure what machine "85.25.195.184" is (reverse dns says it's astra1631.startdedicated.net in Germany), but it's the one used to send emails from "amigans-net@groupmail.com".

The SPF record for "groupmail.com" is:
v=spf1 redirect=mail.com

Which apparently means it uses the SPF record of "mail.com" instead:
v=spf1 ip4:213.165.64.0/23 ip4:74.208.5.64/26 ip4:74.208.122.0/26 ip4:212.227.126.128/25 ip4:212.227.15.0/24 ip4:212.227.17.0/27 ip4:74.208.4.192/26 ip4:82.165.159.0/24 ip4:217.72.207.0/27 -all

And since that doesn't contain 85.25.195.184 (and end's with -all), amigans.net emails are classed as spam.