[kwlug-disc] About email, SPF, question

[Mikalai Birukou]

We currently have thread, where one of receiving servers keeps adding 
"[Possible phishing attempt]" into subject. It happens on my posts.

Is it possible that kwlug.org sender isn't in my domain's SPF, and this 
triggers such labeling?

My domain is setup to the t, like protonmail asks one to set things up. 
In fact, they generate DNS records for you to copy and paste (convenient 
admin ux).