About the Microsoft Exchange connector

The Microsoft Exchange connector lets you connect your Microsoft 365 or Exchange Online email servers directly, enabling secure email traffic with your domain's services. It uses the Microsoft Graph API and OAuth for secure communication and supports email conversion to tickets. Note limitations like email size and rate limits. Avoid altering critical email headers to maintain message integrity.


The Microsoft Exchange connector allows you to connect your non-Zendesk email servers,
based on Microsoft Exchange, directly to your Zendesk Support instance. This is ideal
for Microsoft customers looking to connect their online Microsoft 365 or Exchange
servers and leverage their Exchange and Outlook workflows.
The main advantage of this solution is that it allows you to send and receive email
traffic to and from your customers using your domain’s email services, while ensuring
encrypted and secure relays to and from Zendesk.
Microsoft Exchange is the server powering all Microsoft email products, including
Microsoft 365. Therefore, the Zendesk Microsoft Exchange connector is compatible with
the online version of all Microsoft email products. The connector is incompatible with
Exchange Server on-premises. If you're using on-premises servers, the SMTP connector may be a better option.
See Connecting your Microsoft Exchange account to
Zendesk for more information on establishing and managing your
connections.
This article includes the following topics:

Understanding how email is transmitted with the Exchange connector
Technical details
Requirements
Limitations
Understanding the email labeling system
Considerations regarding email headers



Understanding how email is transmitted with the Exchange connector

Using an Exchange API, the Microsoft Exchange connector allows you to fetch email
from an Exchange inbox and automatically convert email messages to tickets. The API
is also leveraged to deliver outbound email from Zendesk to your Exchange mailbox.

Zendesk Support frequently checks for new email in your Exchange inbox. Only new,
unread email messages in the inbox will be converted into tickets. Ticket
notifications will be sent from your Microsoft email address.



Technical details


The Exchange connector uses the Microsoft Graph API for communication with
Microsoft.
All communication between Zendesk and the Exchange server is conducted through
HTTPS calls.
The Exchange connector uses OAuth for authorization access.
During authorization, you are granting access to Zendesk's verified Azure
application.
Credentials used to access your Exchange mailbox are securely stored and
encrypted at rest.
Zendesk will request only the essential permissions required for the operations
of the Exchange connector:
openid
offline_access
email
User.Read
Mail.Send
Mail.ReadWrite






Requirements


The Zendesk Exchange connector is compatible with Microsoft Exchange Online
only. Exchange Server on-premises versions are not supported.
To connect your Exchange mailbox to Zendesk, you must be able to sign in
(authenticate and authorize) as the account associated with that Exchange
mailbox.
The Microsoft email address cannot be used by any other connection method (such
as email forwarding), agent, or end user in your Zendesk account.
You must use OAuth to authenticate all Exchange API
requests to Zendesk.
You must set permissions on the Exchange mailbox to
control who can access the mailbox and what actions they can perform.
Your Exchange admin must have the ability to grant permissions to Zendesk during
authorization.




Limitations



Due to Microsoft API limitations, personalized email replies don't
work with the Exchange connector. The Microsoft account configuration
determines the sender name on outgoing emails sent from the Exchange
server.

Side conversations don't utilize
the Exchange connector for communication. Instead, emails related to side
conversations are sent directly from Zendesk hosts (it's important to set up
SPF and DKIM records when using external support addresses). Side conversation child tickets
follow the same configuration as other tickets and use the Exchange
connector for communication.
Due to requirements imposed by the Microsoft API, traffic through the
Exchange connector has the following limitations.
Limitations when sending email from Exchange:
30 emails per minute per mailbox (with retries for up to two
hours)
50MB per 5 minutes per mailbox
10,000 different email recipients in a 24-hour period per
mailbox (shared across multiple applications connected to
the mailbox) Microsoft announced that
this limit will be reduced to 2,000 per 24-hour period
for existing customers starting in October
2026.



Limitations when fetching email from Exchange to Zendesk:
25 emails per minute per mailbox
Max email size is 50MB (including attachments)



If you have questions about Microsoft's rate limits, open a ticket
with Microsoft directly. Zendesk doesn't have additional information or
the ability to negotiate higher rate limits.






Understanding the email labeling system

The Microsoft Exchange connector is designed to help you efficiently manage your
inbox by applying labels to inbound emails, allowing you to easily track their
processing status. When emails are processed in Microsoft Exchange, the following
labels are applied:


Zendesk: This label appears on all emails that have been
processed by Zendesk. When only the Zendesk label is present,
it means the email has been successfully imported into your Zendesk
account.
Important: Don't delete the
Zendesk label from the emails in your inbox. Deleting
the label may cause issues with the integration, preventing it from
importing new emails, as it will continuously attempt to re-import older
emails without the label.


RejectedByZendesk: This label appears in addition to the
Zendesk label when Zendesk couldn't import the email
successfully. Emails tagged with both labels were processed but not imported
into your Zendesk account.



When an email might be rejected

There are several common reasons why an email receives the
RejectedByZendesk label:


Email size limitations: Emails exceeding 50 MB cannot be processed.
If your email contains large attachments, consider compressing or sharing
the files through a cloud storage link instead.

Email format issues: Emails with improper formatting, corrupted
content, or invalid structure might be rejected. Verify that all required
fields, such as From and To, are filled
in. Additionally, ensure that the email body and any attachments are intact
and properly uploaded.





Considerations regarding email headers

Email headers (such as To, From,
CC, and Reply-To) contain important data and
metadata about an email message.
Your administrator may want to change email headers for several reasons. However,
it’s important to note that some header fields should never be altered since
they are critical for ensuring the correct delivery and integrity of the message.
Changing standard headers at the account's email domain before outbound sending is
not supported. Any issues that emerge as a result of this should be investigated and
corrected at the external domain.
The below headers should persist throughout the outbound relay process:

Auto-Submitted: auto-generated
X-Auto-Response-Suppress: All
X-Mailer: Zendesk Mailer
X-Zendesk-From-Account-Id: ******
X-Zendesk-Email-Id: ************************

Changing your email header fields doesn’t change how Zendesk works; it only changes
how you send your outbound messages and how you might receive responses. The
relationships between the requester, agents, and CCs in the email and subsequent
ticket should not change.


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