Directories - Domain Types

Mimecast maintains the domains you register as internal, as well as the external domains with which your organization exchanges email. This article describes the different types of email domains that Mimecast maintains.

Internal Domains

An internal domain is a domain that your organization has registered with Mimecast to send, receive, and/or archive email for.

To list your internal domains:

1. Log in to the Mimecast Administration Console.
2. Select the Users & Groups | Internal Directories menu item.

Internal domains fall into the following types, as signified by the icon on the right-hand side:

Internal Domain Type	Icon	Description
Remote		A domain is considered remote if the mailboxes for users with email addresses in the domain are stored on any infrastructure other than Mimecast (e.g., Microsoft Exchange On-Premise or Microsoft 365). Inbound emails received from a user with an email address in a remote domain are delivered to your organization's email infrastructure via SMTP. Outbound emails can be sent from a user with an email address in a remote domain, from your organization's email infrastructure via Mimecast.
Local		Local domains are typically used by customers without internal email infrastructure. A domain is considered local if Mimecast maintains the mailboxes for users with email addresses in the domain. Inbound emails received from a user with an email address in a local domain, are kept in the Mimecast infrastructure and need to be accessed using POP3. Outbound emails from a user with an email address in a local domain can be sent directly via Mimecast using an authenticated SMTP connection. Only Mimecast Support can set a domain to be considered local.
Send Only	N/A	This option allows your organization to send outbound emails from a domain but not receive inbound emails to the domain. A send-only domain could be used when your organization is sending email on behalf of another Mimecast customer. Users with an email address in a send-only domain cannot login to Mimecast applications.   Only Mimecast Support can set a domain to be considered send only.

External Domains

A domain is considered external if it is not one of your Mimecast-registered Internal Domains. They are automatically added to your service when an outbound email is sent by an internal user.

To list your external domains:

1. Log in to the Mimecast Administration Console.
2. Select the Users & Groups | External Directories menu item.

If your organization uses the Secure Messaging feature, external domains are used to facilitate authentication for recipients of confidential email.