Zendesk Support

Zendesk Support has a Microsoft Exchange connector that sends and fetches a support address's email through one of your Microsoft 365 mailboxes, and Footer365 signs mail that passes through your Microsoft 365. Choose how your CRM or app sends its mail explains the two ways to send, and this guide follows the first.

At a glance

• Can be signed: ticket email sent through the Microsoft Exchange connector. Zendesk says: "Ticket notifications will be sent from your Microsoft email address." and that the connector's API "is also leveraged to deliver outbound email from Zendesk to your Exchange mailbox."
• Cannot be signed: anything Zendesk sends from a support address that has no connector, and ticket email from an address whose connector is disconnected, because Zendesk says "outgoing email is not sent from that address" and does not fall back to another connection.
• How it connects: "The Exchange connector uses the Microsoft Graph API for communication with Microsoft." It is compatible with Exchange Online only.
• Status: from Zendesk's documentation as read on 23 October 2026, not tested by Footer365.

Before you start

• Footer365 mail flow is set up. With the Outlook add-in only, no mail Zendesk sends is signed. Using the Outlook add-in only
• The connected mailbox has a Footer365 signature rule that covers it.
• Zendesk says you must be a Zendesk administrator to connect an Exchange account, and lists the Team, Professional and Enterprise Support plans.
• Your Exchange administrator must be able to approve Zendesk during authorisation. Zendesk says: "Your Exchange admin must have the ability to grant permissions to Zendesk during authorization."

Step 1: Approve the app in Microsoft 365

Zendesk asks for these permissions: openid, offline_access, email, User.Read, Mail.Send and Mail.ReadWrite. The person who connects the mailbox approves them on Microsoft's screen, if your organisation lets them, or an administrator approves them. Approve an app's access in Microsoft 365

Step 2: Choose the mailbox

One Microsoft 365 mailbox is connected for each support address.

• A user mailbox works directly. The mail is signed with the signature your rules give that mailbox, so a support address needs a rule of its own.
• A shared mailbox: Zendesk says you "must first convert the shared mailbox into a regular user mailbox." After conversion it can have a password like any other user mailbox. Once converted, give it a signature rule like any other mailbox.
• Zendesk says the mailbox must not also be used by another connection method, such as email forwarding.

Step 3: Connect it in Zendesk

A Zendesk administrator does this:

1. In Admin Center, select Channels, then Talk and email, then Email.
2. Select Manage support addresses, then Add address, then Connect external address.
3. If you have more than one brand, choose the brand. Choose Microsoft Exchange connector, then select Next.
4. Choose whether to create tickets from the last 300 emails. Zendesk says that imports "the 300 most recent emails in your account as tickets, regardless of whether they've been read", and that it can take up to 15 minutes. Deselect it if you do not want old email imported.
5. Select Accept on Microsoft's screen, then Done.

Zendesk's own steps: Connecting your Microsoft Exchange account to Zendesk.

Step 4: Check one message

1. Reply to a test ticket from an address outside your organisation, or send a ticket notification.
2. Open the headers of the copy you receive.
3. Return-Path should be the connected mailbox's address, and X-Footer365-Relay-Id should be there.
4. Look in the connected mailbox's Sent Items. Zendesk's page makes no statement about Sent Items, so its absence is not a fault by itself.

What other results mean: Mail from our CRM is not signed.

Where the signature goes

Zendesk's pages read do not describe a signature setting for connector email, and say that personalised email replies do not work with the connector. If you see two signatures, remove any signature Zendesk adds in its email templates. To place Footer365's signature in a template, use a marker, and check one message, because Zendesk's pages do not say what it does with text in double braces. Place the signature with a marker

What is not signed

• Anything sent without a connected address, because the pages read do not say which servers Zendesk Support sends from in that case. Check one message.
• Replies and automation email: the page says ticket notifications are sent from your Microsoft email address, and does not mention triggers or automations, so check one of each kind you rely on.

What stops working

• The authenticated SMTP connector. Zendesk says: "customers using Microsoft Exchange should use the Zendesk Exchange connector instead of the SMTP connector", "Due to Microsoft Exchange Online retiring Basic authentication for SMTP at the end of December, 2026". If you set up the SMTP connector for a Microsoft mailbox, move to the Exchange connector. Turn on SMTP sign-in for one mailbox
• Zendesk Sell. Zendesk announced on 9 September 2025: "After careful consideration, we've made the decision to retire Zendesk Sell on August 31, 2027." Zendesk says Sell connects Microsoft email with OAuth by default, and asks you to make sure the SMTP protocol is enabled in your Microsoft 365. This guide does not cover Sell, so do not start a new Sell setup.

Limits

Zendesk gives these limits for sending from an Exchange mailbox, per mailbox:

• 30 emails a minute, with retries for up to two hours.
• 50 MB per five minutes.
• 10,000 different recipients in 24 hours, shared across the apps connected to the mailbox.

Zendesk says it cannot negotiate higher limits, and that questions about them go to Microsoft. Microsoft's own limits are 10,000 recipients a day and 30 messages a minute for a mailbox. Microsoft: Exchange Online limits

Last resort: a connector to Exchange Online

Zendesk's Microsoft Exchange connector is not a connector you create in Exchange, and the pages read describe no other route into Exchange Online. Zendesk's authenticated SMTP connector is for "a non-Zendesk email server", and for Exchange Online Zendesk points to the Exchange connector instead. Microsoft says SMTP relay cannot be used for a service hosted by someone else. So a Zendesk address without the Exchange connector cannot be signed. Last resort: a connector to Exchange Online

If it does not work

1. Zendesk cannot connect. Check the Exchange account is Exchange Online and a user mailbox, and that you are a Zendesk administrator. Zendesk says the connector is compatible with Exchange Online only.
2. Microsoft says "Need admin approval". Approve an app's access in Microsoft 365
3. The message has no X-Footer365-Relay-Id. It did not pass through Microsoft 365.
4. It passed through Footer365 but is unsigned. The connected mailbox probably has no rule. The wrong signature is used for a shared mailbox or delegate
5. Still not clear. Mail from our CRM is not signed

Sources

Read on 23 October 2026:

• Zendesk: About the Microsoft Exchange connector, no date shown.
• Zendesk: Connecting your Microsoft Exchange account to Zendesk, no date shown.
• Zendesk: About the authenticated SMTP connector, no date shown.
• Zendesk: Connecting your email with Zendesk Sell, no date shown.
• Zendesk: Announcing the retiring of Zendesk Sell, published 9 September 2025.