According to the HP Forum: https://h30434.www3.hp.com/t5/Printers-Archive-Read-Only/What-ports-to-open-on-ADSL-router-for-ePrint/td-p/457327 You should allow (outbound): 5222 (for XMPP protocol) 443 (for HTTPS protocol) In order to use ePrint. Thus, I would check the logs in order to see what's going on. Maybe you can trace the network traffic using the MX and/or Wireshark
... View more