I have a CentOS 7 server that is running Exim and Dovecot for communicating on SMTP and POP3 ports. I want to configure them to use TLS to encrypt all data. I have already figured how to change the config files of Exim and Dovecot, but there is one problem: the certificates I intended to use are self-signed and it seems that gmail does not accept SSL certificates that are self-signed.
Now I want to buy a DV SSHL certificate from a trusted authority, but I don't know which subdomain I should buy it for. My DNS records include an MX record that says "10 mail" and then it is assigned to the IP address of my server. I don't know what 10 means there, but I suppose that means mail.domain.tld is the address of my mail server. Right?
So, here are my questions:
- Should I get a certificate for mail.domain.tld?
- Can I use my certificate for domain.tld which has been issued by a trusted authority?
- Can I get a certificate for an IP address instead of a FQDN? Will that work with gmail too?