In the past I would do the following:
mail.externaldomain.com
autodiscover.externaldomain.com
autodiscover.internaldomain.local
servername.internaldomain.local
You can no longer include .local in the certificate as seen in the posts below:
https://www.cabforum.org/Baseline_Requirements_V1.pdf
I've been setting all of EWS, OWA, autodiscover internal FQDN to use the external FQDN. Has anyone else been using another system for this? Thanks in advance.