What are alternatives to spending $$$ on Mailgun? They recently ended their free tier of service for under 50,000 messages, and sending emails has started costing us real money.
I've used https://mailinabox.email/ personally and it includes a very easy setup for DKIM etc. SMTP authentication and anti-spam measures. Sending email out through such a box would be one possibility.
Would https://www.proxmox.com/en/proxmox-mail-gateway work?