SMTP and certificates

We’re trying to use the SMTP feature within Octopus (running but we’re running into an issue regarding certificates. We receive the following error message and I’m just unsure where to start:

The remote certificate is invalid according to the validation procedure.
System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.
at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, Exception exception)
at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) …

The error message refers to the “remote” certificate but does that imply the mail server from which SMTP is attempting to use, or is the Octopus Server’s certificate the “remote” one from the mail host? We have a valid certificate for our Octopus server. Any thoughts or suggestions would be helpful. Thanks!

Could this be a certificate installation issue on the Octopus server? Maybe not installed in the right folder for Certificate manager?

Hi Ian,

Thanks for getting in touch!

It looks like this error is with the remote mail host not having a valid certificate and Octopus is rejecting it because of this.
You will need to get a valid certificate on the remote SMTP server.

Hope this helps!


Thanks, Vanessa! I’ll try to test this out and get back to you with the results.

We were able to get SMTP to work, but it was largely a configuration issue with our Octopus Server to send mail through our internal SMTP services.

Thanks, Vanessa!