Mailman3 users --
I am in the process of migrating a set of mailing lists from a very old privately operated server running mailman2 to a VM in Google's cloud (GCP) running mailman3.
I have mailman3 up and running in GCP. However, VM's in GCP are not permitted to send emails. To work around this I configured postfix relay SMTP traffic through sendgrid.com. I chose Sendgrid because they offer a free service for low volume users. This works well for emails generated by the mailman3 system. However, it does not work for the list traffic itself.
Sendgrid requires that the "From:" address on any email reference an authenticated domain.
In the old mailman2 implementation, emails sent by mailman are listed as
From: <human name via LISTNAME> LISTNAME@LISTDOMAIN.org
Reply-to: <human name> sender@senderdomain.com (the original email's sender)
Sendgrid would be happy with this, because LISTDOMAIN.org is a validated domain.
However, in my mailman3 implementation, the From: header lists the original email's sender. Sendgrid rejects this because the original email's sender's address is not one of the validated domains.
How do I configure mailman3 to generate headers in the same style as the old mailman2 implementation?
Thanks!
-- Stephen Daniel