SSL cert for public IBE portal

[forti18]

This is most likely a stupid question, but my knowledge of certificates is lacking!

I've installed an internally-signed SSL certificate on our FortiMail pair for internal clients connecting to FortiMail Webmail (for quarantine portal), and this works fine, certificate is accepted by browsers.

I've just began looking at testing IBE, with the Webmail page being publicly accessible for registration/message pickup, and I'm unsure how to apply a public SSL certificate for this connection which maintaining the internal certificate. I have a valid certificate and private key file uploaded already to the FortiMail for the URL, but I believe any clients connecting externally are seeing the internal domain CA signed cert, which is set as default.

Is it possible to have separate certs for the Webmail URL based on whether it is accessed internally or externally? Our internal and external domains are different. 

[Bromont_FTNT]

The HTTPS certificate is the same for both webmail and IBE

[forti18]

Bromont wrote:

The HTTPS certificate is the same for both webmail and IBE

Thanks. So how are people treating SSL certificates when internal and external domains are different (and with it not being possible to own the external domain name of our internal domain)?