Hi @ Susan Dodds,
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For Exchange SERVER to install SAN certificates, the minimum hostname you need is:
1. mail.domain.com: This is the common name of the certificate and the primary host name that clients will use to access Exchange services.
2. autodiscover.domain.com: This is the host name that Outlook and other clients use to discover Exchange configuration and settings.
3. server.domain.local: This is the internal host name of the Exchange server, which may be required in some cases.
If you want to support multiple primary email addresses for users, you can also add additional host names for each SMTP domain that you own.
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