Cisco Unity Connection to SMTP Relay TLS connection

[abdelaziz.arnous]

Hello Guys,

I have a customer who wants to enable "tls encryption" option on Windows relay server and when he is enabling this option the voicemail messages cannot be sent as email but if he removed this option from the Windows server the voicemail messages will be sent successfully to the user outlook mailbox.

Is there any option on CUC server to enable TLS with the SMTP relay server so connection can be secured?

Thanks.

[Jonathan Schulenberg]

I haven’t tried this but here are a few tips to get you started:
1. If you run a packet capture from CUC (https://community.cisco.com/t5/collaboration-voice-and-video/packet-capture-on-cucm-appliance-model/ta-p/3118507), what does the PCAP show happens on the SMTP transmission? Does the smart host still accept a connection on port 25? Does it tell the SMTP client to STARTTLS? Does CUC comply? Does that TLS handshake fail?
2. If the you see a TLS handshake alarm from CUC the most likely reason is that the certificate chain presented by Exchange is not trusted by CUC. You need to upload the issuing chain to Tomcat-trust and maybe Connection-trust followed by a restart.