POSTFIX delivery temporarily suspended: Server certificate not trusted

Hi after updating to the latest ISPconfig i get this error to one client only. Before i point the finger i would like to know if this is a known issue? i checked main.cf and run a diff tool over the backedup one and the new and there is no change in file. The cert using is the one that ispconfig install generated and is valid according to my webmail who uses the same cert.

Code:

delivery temporarily suspended: Server certificate not trusted

 

Is the error message about arriving or outgoing e-mail?
Use Internet Search Engines with

Code:

ssl testing mail server

to find tools to check certificate e-mail server is using.

 

Mine was all green already tested everything on my side, but because i update to the latest version i just wanted to make sure that i didnt miss anything on the change that came with the last version (custom config for postfix and dovecotetc). It was SSL mismatch
on their side.