CentOS 5 | SendMail
Can TLS certificates be shared between multiple sendmail MTAs? I'm using a CA-signed cert and would prefer to not purchase new certs for each additional sendmail host.
Most likely not, if your certificate is not wildcard one (has * in the host name). I assume your hosts are actually named differently, right?
The only way I can think of will be able to use it is to terminate TLS on a load balancer put in front of the multiple sendmail hosts.
Of course all of the above is predicated on the clients doing real verification on the certificate. If they ignore the name mismatch issue, then you can use it without a problem, but it will get you no real security, as MiTM can intercept such connections.
Certificates can always be shared between different hosts; as long as you have their private keys, you can always copy them to other servers (otherwise, how could you rebuild a server in a disaster recovery scenario?).
This is quite common f.e. for load balanced web servers; SMTP with TLS is in no way different from that.