Sent an email in to support as well, but also posting here to increase visibility, it’s something the domain admins for alta.inc need to look at.
Causes a “This email has failed its domain’s authentication requirements. It may be spoofed or improperly forwarded” Warning in my webmail client.
Do you have more info? We have DMARC and SPF set up properly, and Google accepts it
Mxtoolbox shows you have no DMARC policy set, it might be that the webmail is getting upset about.
Can you send me an email with your original headers to firstname.lastname@example.org ?
Think I copied them all but on mobile at the moment so if not let me know and I’ll do it again tomorrow when I’m at a computer