Thursday, March 5, 2026
Tip of the Day: Using Custom URI Port Range with OAuth2
Product: R:Mail 11
Build: 11.0.3.20226 or higher
Section: Plugins
Keywords: OAuth, Redirect URI, Port, Tenant ID
R:Mail 11 supports OAuth 2.0 authorization for R:BASE applications that
send email through Google and Microsoft Azure services. OAuth 2.0 allows
applications to access API resources on behalf of a user without
requiring the user’s credentials to be shared with the application.
Redirect URI Port Range
When configuring OAuth 2.0, a Redirect URI must be specified so that
R:Mail can complete the authentication process and send email messages
through a local redirect port. By default, R:Mail uses the following
port range: 2132 – 2136
When sending email, R:Mail scans this range and selects the first
available port. Because of this, a maximum of five simultaneous R:Mail
application instances using OAuth 2.0 can send email at the same time on
a single machine.
In environments with Remote Client installations or a large number of
R:Mail users, the default five-port range may be exceeded, which can
result in port conflicts. To address this, R:Mail now supports defining
a custom redirect port range.
*Custom Redirect Port Range*
The desired ports must first be defined in the Redirect URI list within
the Google or Microsoft Azure API configuration portal. After the
Redirect URIs are configured, the same port values must be specified
within the R:BASE application using the new ADD_OAUTH2_REDIR_PORT parameter:
ADD_OAUTH2_REDIR_PORT
Specifies redirected port values. The ports should be provided as a
comma-separated list.
Example:
PLUGIN RMail vPort|ADD_OAUTH2_REDIR_PORT 2140, 2141, 2142, 2143, 2144
Important: The ports listed in ADD_OAUTH2_REDIR_PORT must also be
included in the Redirect URI configuration within the Google or
Microsoft Azure API portal.
*Microsoft Azure Tenant ID Support*
R:Mail has also been enhanced to support Tenant ID values when accessing
Microsoft Azure API resources. The Tenant ID, also known as the
Directory ID, identifies the organization associated with the Azure
application. Some Microsoft Azure APIs require the Tenant/Directory ID
to be specified as part of the authentication request. This value can
now be provided in R:Mail using the new OAUTH2_TENANT_ID parameter.
OAUTH2_TENANT_ID
Specifies the Microsoft Azure Tenant (Directory) ID. If a Tenant ID is
not specified, R:Mail will automatically use the Microsoft common endpoint.
The Support Team
R:BASE Technologies, Inc.
https://www.rbase.com
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