Email signature for shared email box

Question

We would like to configure an email signature for a shared mailbox so that when an email is sent by selecting the shared mailbox address in Outlook, the signature is added by default.

I have tested this in OWA, and when the shared mailbox is opened as “Open another mailbox,” the signature works as expected. However, when sending an email from the primary mailbox and selecting the shared mailbox address in the From field, the signature is not applied.

Please let me know if this is possible to achieve and, if so, what configuration or workaround can be used.

Answer 1

Hi Sanjay Bhakuni,

Thank you for posting your question in the Microsoft Q&A forum.

It’s possible that when you compose a message in the Outlook/OWA session of your primary mailbox and then change the From address to the shared mailbox, you are still operating within the primary‑mailbox session. Consequently, the primary mailbox’s settings (including signature behavior) are applied, so the shared mailbox’s signature does not get inserted automatically.

Besides Vasil’s suggestion above, a practical workaround is to use an Exchange Online mail flow (transport) rule to append a signature for messages sent from the shared mailbox. Microsoft documents this approach here: https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/disclaimers-signatures-footers-or-headers#how-do-you-know-this-worked

However, there a few considerations and limitations to keep in mind with server-side disclaimers:

• Avoiding duplicate inserts: Add an exception that looks for a unique text marker in your disclaimer/signature so it isn’t added multiple times in the same conversation.
• Formatting & images: Server‑side disclaimers cannot embed images; they only insert HTML that can reference images via an absolute src URL. Host your images on a publicly accessible HTTPS location (e.g., a CDN, a publicly accessible SharePoint site, or your own web server) and use full URLs. Be aware that some recipients’ mail clients may block external image downloads by default.

For more about transport rule: https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/mail-flow-rule-actions

I hope this suggestion is helpful. If you have any further questions, please feel free to share.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".     

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

This is expected behavior in Outlook.

When you open the shared mailbox directly (OWA → Open another mailbox), Outlook loads that mailbox’s settings — including its signature. But when you send from your primary mailbox and just select the shared address in the From field, Outlook still uses your primary profile, so the shared mailbox signature isn’t applied.

Unfortunately there’s no native setting in Outlook or Exchange to automatically apply a shared mailbox signature in that scenario.

Open the shared mailbox as a separate account/profile in Outlook (so its signature loads normally)

Use a mail flow rule in Exchange to append a basic footer (limited formatting)

• Use a centralized signature tool like MySignature that applies signatures based on sender or alias, including shared mailboxes

Most teams that rely heavily on shared inboxes go with the last option because it avoids manual switching.

Answer 3

HI Sanjay, happy new year. It is possible, but that, and many other features are only available when accessing the shared mailbox in "direct" mode. You have already found how this works with OWA, similar behavior can be observed in the desktop Outlook client. In order to access this feature, you must configure the shard mailbox as additional account, that is add it via FIle > Add account. Here are detailed instructions:

Classic Outlook: https://michev.info/blog/post/3567/how-to-add-a-shared-mailbox-as-additional-account-in-outlook-2022-version

New Outlook: https://michev.info/blog/post/6736/how-to-add-a-shared-mailbox-as-additional-account-in-the-new-outlook

Once you do that, you will be able to access signature, auto-replies, rules and more.

Answer 4

To configure an email signature for a shared mailbox in Outlook, you can use the Set-MailboxMessageConfiguration cmdlet. This cmdlet allows you to set the email signature for specific mailboxes, including shared mailboxes. However, it is important to note that the settings applied through this cmdlet are specific to Outlook on the web and may not automatically apply when sending emails from the primary mailbox while selecting the shared mailbox in the From field.

If the signature does not apply when sending from the primary mailbox, it may be necessary to set the signature directly on the shared mailbox itself. This can be done by accessing the shared mailbox settings and configuring the email signature there.

Additionally, ensure that the shared mailbox is properly set up and that users have the necessary permissions to manage its settings. If issues persist, consider checking the configuration of the shared mailbox and the permissions assigned to users.

---

References:

• Set-MailboxMessageConfiguration
• Configure shared mailboxes in new Outlook