Palo Alto Decrypt Policy Is Breaking Your Printer — Why Print Traffic Gets Caught and How to Add the Right Exception
Joe B.
Reviewed for technical accuracy
Specialities: Palo Alto NGFW & SSL decryption, print servers (Windows / CUPS), IPP/IPPS & SMB printing, MFP scan-to-email, policy-based decryption exceptions for business apps
Fix “Palo Alto decrypt policy breaks print” — add SSL decryption exceptions for print servers, MFPs, and HTTPS print portals
Technician
When decryption is turned on, the firewall becomes a “man in the middle” for TLS. That’s great for inspecting web traffic, but some print drivers, MFP firmware, or vendor cloud print portals don’t like being intercepted — they use things like certificate pinning, mutual TLS, or odd cipher suites. The result is exactly what you’re seeing: jobs get stuck in the queue, users get “cannot connect to printer” or “SSL handshake error”, and it looks like the printer is broken when it’s actually the decrypt policy.
To aim you at the right decryption exception, I need to narrow it down a bit: are we talking about Windows print server queues, direct IP printing to an MFP, or a secure web print portal (for example, pull-print or SAP over HTTPS)? And do you see any decrypt-error or unsupported messages for that traffic in the Palo Alto logs?
Technician
Here’s what typically happens:
1) You deploy SSL Forward Proxy with a root CA, so browsers and normal HTTPS apps are fine after you push the cert.
2) The print server web portal or the MFP’s secure channel expects to talk directly to its own certificate and may use certificate pinning or mutual TLS.
3) When the Palo Alto decrypt policy intercepts that connection, the MFP or print driver sees the firewall’s “fake” cert instead of the original and refuses the handshake, which looks like random print failures or jobs stuck in a “processing” state.
The fix is not to kill decryption globally, but to carve out a targeted SSL decryption exception (no-decrypt rule) or add the print infrastructure to the SSL Decryption Exclusion list. That way, the firewall still inspects everything else, but your print traffic stays encrypted end-to-end and works again.
Technician
• A policy-based “no-decrypt” rule in Policies → Decryption. You match traffic (source, destination, URL category, user, etc.) and set the action to “No Decrypt”. This is ideal for excluding print servers, MFP IP ranges, or specific URL categories tied to printing.
• The SSL Decryption Exclusions list under Device → Certificate Management → SSL Decryption Exclusion. This is better when a specific external site or cloud service technically breaks decryption and you just want to say “never decrypt this hostname”.
In your case, I’d generally:
1) Create a dedicated no-decrypt policy rule for print traffic that matches your print server IPs, MFP IPs, and any known cloud print URLs.
2) Place that rule above the general decrypt outbound rule so it’s evaluated first.
3) If you find specific external hosts that always break decryption, optionally add them to the decryption exclusion list as well.
This keeps full SSL decryption for browsers and most apps, while carving out a safe decryption exception for your printing workflows.
Technician
The safer pattern is:
• Match on specific destinations tied to printing (for example, the FQDN of the cloud print service, or the internal print server IP/port), not “any”.
• If possible, constrain the rule by service (TCP 443 or IPPS ports) and URL category used only by the print platform.
• Keep normal user browsing from those devices behind your regular decrypt policy where it still makes sense.
For example, you might create a “No Decrypt – Print Services” rule with:
• Source: MFP subnet + print server subnet
• Destination: print server IP, cloud print FQDNs
• Service: application-default (usually HTTPS/IPPS)
• Action: No Decrypt
Everything else continues to hit your standard decrypt-outbound rule. That way, you fix the Palo Alto decrypt policy breaking printing without turning your print environment into a security blind spot.
Technician
What actually changes is:
• The firewall stops presenting its own forward-proxy certificate for those flows.
• The client and print server/MFP perform a normal end-to-end TLS handshake with the real certificate.
• Any certificate pinning, client-auth, or quirky cipher usage that was breaking decryption is no longer interfered with.
You may still need to:
• Clear stuck print jobs from the queue.
• Close/re-open apps that cached a bad connection.
But you shouldn’t need to redeploy the Palo Alto root CA to clients, because we’re moving that traffic away from decryption. Think of it as telling the firewall, “Inspect almost everything, but do not touch these specific print flows because they rely on strict TLS behavior.”
Technician
If the Palo Alto is decrypting your SMTP-over-TLS or STARTTLS traffic, some mail providers or MFPs may reject the session when they see the firewall’s cert or a cipher mismatch. The fix is to:
• Identify the SMTP server FQDN / IP used by the printers.
• Add it either to a no-decrypt rule (matching the printer subnets to that mail host on TCP 587/465/25 as appropriate).
• Or add the mail host to the SSL Decryption Exclusion list if it’s a third-party cloud mail service that technically breaks decryption.
That way, both printing and scan-to-email traffic for your MFPs bypass SSL inspection cleanly, while users’ normal browsing and webmail stay under SSL Forward Proxy.
Technician
Here’s a simple proof-of-concept I use whenever someone says “Palo Alto decryption broke printing”:
1) Pick a single test user + printer queue.
2) Temporarily move that user’s traffic (or the print server IP) into a no-decrypt rule above your main decrypt policy.
3) Commit, then immediately print a test job that was failing before.
4) Watch the Traffic / Decryption logs: you should now see those sessions marked as “not decrypted” but allowed, and the print job should complete normally.
If printing works under no-decrypt and fails again when you revert to the general decrypt rule, you have clear evidence that SSL inspection is the cause. You can then refine the policy into a narrow, permanent exception for print services instead of a blanket bypass.
Technician
1) Identify print flows: list the print server IPs, MFP subnets, and any cloud print / accounting URLs and SMTP servers printers talk to.
2) In Policies → Decryption, create a new rule named “No Decrypt – Print Services”.
3) Set Source to the printer/MFP subnets and print server subnet, Destination to the print servers, cloud print FQDNs, and mail server used for scan-to-email, and Service to application-default (HTTPS/SMTP ports).
4) Set Action to No Decrypt and ensure this rule is placed above the general outbound decrypt rule.
5) Commit, then print and scan test jobs while watching the logs to verify that these flows now show as “not decrypted” and succeed.
If you like, we can also look at the SSL Decryption Exclusion list together and decide whether specific external hosts should be added there for technical reasons. Open the chat and I’ll walk you or your firewall admin through the exact changes on a live Palo Alto GUI.
Technician
If your admin wants a second set of eyes on the decryption rules, exclusion lists, or logs, just open the chat. We’ll review the policies together and make sure print traffic is handled correctly without over-bypassing SSL inspection.
Quick answer: the accepted fix
Accepted fix when a Palo Alto decrypt policy breaks printing: identify print servers, MFP subnets, and cloud print / mail hosts, then create a no-decrypt decryption policy rule or targeted SSL decryption exclusion for those flows. Place that exception above the general decrypt rule so print and scan-to-email traffic bypass SSL inspection while the rest of your users stay fully decrypted and inspected.
Why Palo Alto SSL decryption can break print servers and MFPs
When you enable Palo Alto SSL decryption (SSL Forward Proxy) for outbound traffic, the firewall terminates TLS and re-encrypts it to inspect content. Many business apps handle this just fine once the enterprise root CA is deployed. However, print drivers, MFP firmware, secure pull-print portals, and scan-to-email workflows sometimes rely on pinned certificates, mutual TLS, or limited cipher support. If the firewall intercepts these secure sessions without a decryption exception, the result can be failures that look like random printer issues: jobs stuck in queues, “cannot connect to server” errors, or SMTP auth failures. In reality, the decrypt policy is in the middle of the TLS handshake and the device refuses it.
How to verify a decrypt policy is causing your print failures
To confirm that Palo Alto SSL decryption is the reason print jobs fail, temporarily move a test user or print server into a no-decrypt rule above your main decrypt policy. Commit, then send a job that previously failed. If the job now prints successfully and the session is logged as “not decrypted”, you’ve proven that the decrypt policy breaks print and a permanent decryption exception is needed. You can then refine this into a narrow, production-ready print exception that only bypasses SSL inspection for the required hosts and services.
Palo Alto decrypt policy & printing — quick tips for safe exceptions
Don’t disable SSL decryption globally. Use targeted no-decrypt rules and exclusion lists for print traffic.
Quick path: list your print servers, MFP networks, cloud print portals, and mail hosts used by printers. Create a “No Decrypt – Print Services” policy matching only those flows and put it above your general decrypt rule. If specific external sites still break decryption, add them to the SSL Decryption Exclusion list rather than broadening the bypass. This way you fix the Palo Alto decrypt policy breaks print problem while keeping strong visibility and threat prevention for normal web traffic.
Disclaimer: This information is AI-generated and intended for general guidance only. Always follow your organization’s security policies and Palo Alto Networks best practices when changing decryption or exception rules. For advice specific to your firewall version, licensing, and compliance requirements, please consult a verified expert on Whizz-Tech before applying changes.
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FAQ
Why did printing break right after enabling Palo Alto SSL decryption?
When you enable SSL Forward Proxy, the firewall intercepts TLS and presents its own certificate. Many print servers, MFPs, and print drivers don’t expect this and may use certificate pinning or unsupported ciphers. The TLS handshake fails under the decrypt policy, so print jobs and scan-to-email sessions break until you create a no-decrypt exception for those flows.
How do I create a decryption exception so Palo Alto does not break printing?
In Policies → Decryption, add a rule above the general decrypt policy that matches your print server IPs, MFP subnets, and print-related destinations, then set the action to No Decrypt. Optionally, add specific external hosts to the SSL Decryption Exclusion list. Commit, then test printing; those flows should now be allowed without SSL inspection.
Is it safe to exclude print servers and MFPs from SSL decryption?
Yes, if done narrowly. Scope the no-decrypt rule to the exact print hosts, ports, and URLs needed for printing and scan-to-email. Leave user browsing and other traffic under full SSL decryption and security policy. This balances print reliability with strong security elsewhere.
Should I turn off SSL decryption entirely if it breaks printing?
No. Turning off SSL decryption globally removes valuable visibility and threat prevention. It’s better to keep your decrypt policy for general web traffic and create a small, targeted decryption exception for printing so only those flows bypass SSL inspection.
Sources
- Palo Alto Networks — Exclude a Server from Decryption for Technical Reasons
- Palo Alto Networks — Decryption Exclusions Overview
- Palo Alto Live Community — How to Exclude IP Address or Application from SSL Decrypt
Filed under: Network security / VPN / office policies (advanced)
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