Since last week, we no longer receive emails on the ticket server. We use Microsoft Mail Server Office365. We use an Reverse proxy server.
upstream prematurely closed connection while reading response header from upstream, client: 10.56.65.51, server: zammad.g-i-m.com, request: “GET /ws HTTP/1.0”, upstream: “http://127.0.0.1:6042/ws”, host: “zammad.g-i-m.com”
Steps to reproduce the behavior:
Did you setup the account on the “Microsoft 365” menu entry? If not, maybe you run into a deactivated* basic auth, and you have to use the modern auth from the MS365-menu.
*MS randomly deactivate the basic auth from some tenants before the EOL in Oct. 22 is reached.
BTW: You can request to re-enable basic auth and extend the deadline until 1.1.2023 if you need more time to make the switch.