SMTP stops working as expected after PAN-OS upgrade

• SMTP issues started after the PANOS upgrade.
• Random emails are being lost
• SMTP packets with a large client hello are not processed properly
• StartTLS traffic in general
• This issue can occur when a session ingresses the firewall with a large "ClientHello" message fragmented across multiple, potentially out-of-order, packets, and the firewall policy is not configured to decrypt the session.

• PANOS 10.1.x
• PANOS 10.2.x
• PANOS 11.1.x
• PANOS 11.2.x
• SMTP
• Decryption 

Software Issue.

1. The issue is being addressed under PAN-279746
2. The fix will be included in the following and above PAN-OS versions of 10.2.14, 11.1.8, 11.2.6, 11.2.8, 11.1.11, 10.2.17, 10.2.13-h5, 11.1.6-h4, 11.1.4-h14, 10.2.8-h22, 10.2.10-h16, 11.2.4-h6, 11.1.7-h2, 10.2.11-h14, 10.2.7-h28 
   
   

The issue can be resolved by creating an application override to bypass the problematic packet combination behavior.