How to configure shared mailboxes to work with CodeTwo signatures

Problem:

You want to learn how to configure Microsoft 365 shared mailboxes for use with CodeTwo Email Signatures 365.

To learn how to set up CodeTwo to add signatures to shared mailboxes, see this article.

Solution:

You can set up the following types of CodeTwo signatures for shared mailboxes:

Outlook (client-side) signatures – added directly to an email as you compose it in Outlook.
Cloud (server-side) signatures – added after an email is sent.

However, Microsoft 365 shared mailboxes need to be correctly configured to work with our service. Complete the following steps, depending on what signature mode you use in CodeTwo Email Signatures 365:

Outlook (client-side) mode:

Configure users' delegate permissions (Send as / Send on behalf) for a shared mailbox
Add the necessary details to shared mailbox properties (Entra ID attributes)
Include a shared mailbox in CodeTwo's scope of licensed users

Cloud (server-side) mode:

Configure users' delegate permissions (Send as / Send on behalf) for a shared mailbox
Add the necessary details to shared mailbox properties (Entra ID attributes)
Include a shared mailbox in CodeTwo's scope of licensed users
Include a shared mailbox in CodeTwo's Exchange transport rule
Enable message copying to the Sent Items folder of a shared mailbox

If you use combo mode, refer to the steps that apply to the types of signatures you use in your organization (cloud or Outlook signatures).

Configure users' delegate permissions (Send as / Send on behalf) for a shared mailbox

Refer to this article to learn how CodeTwo adds signatures to emails sent by users with different delegate permissions.

To grant the delegate permissions to chosen users, you need to:

Sign in to the Exchange admin center with your Microsoft 365 global admin or Exchange admin account.
Go to Recipients > Mailboxes and select a shared mailbox for which you want to configure the delegate rights:
1. To grant the Send on behalf permission to the shared mailbox, click Send on behalf (Fig. 1.) and select the desired users with the user picker. Save your changes by clicking Save > Confirm.

Fig. 1. Configuring the Send on behalf permissions for a shared mailbox.

To grant the Send as permission, go to the Delegation tab, click the Edit button in the Send as section (Fig. 2.) and choose the desired users with the user picker. Save your changes by clicking Save > Confirm.

Fig. 2. Configuring the Send as permissions for a shared mailbox.

After a few minutes, the shared mailbox folders will appear in delegated users' Outlook apps. They may need to restart their Outlook.

Add the necessary details to shared mailbox properties (Entra ID attributes)

If you plan to use placeholders in the signature template, keep in mind that shared mailboxes typically don't have contact or personal details filled in Entra ID (Azure AD). To prevent missing information in the signature, add the necessary details by editing the mailbox properties in the Exchange admin center or by using CodeTwo's Attributes manager. For example, to display a team name (e.g. Customer Support), you can enter it in the First Name attribute and leave the Last Name attribute empty to achieve the result shown in Fig. 3.

Fig. 3. An example configuration of the First name placeholder for a shared mailbox.

Include a shared mailbox in CodeTwo's scope of licensed users

This step is required if your users send emails as a shared mailbox. In such a scenario, a shared mailbox is treated by CodeTwo as a separate user and needs to be assigned a license.

The Scope & region setting allows you to choose which users (mailboxes) you want to license to use CodeTwo. You can either select all users in your Microsoft 365 tenant or limit licensing to users belonging to a selected group (Microsoft 365 group, distribution list, or security group), as shown in Fig. 4. Learn more about this scope

Fig. 4. Here you can limit the scope of licensed CodeTwo users to members of a specific group only.

If you've limited the scope of licensed users to a selected group, as shown in Fig. 4., be sure your shared mailboxes are added as members of this group. Here's how to do that:

Sign in to the Exchange admin center with your Microsoft 365 global admin or Exchange admin account.
Go to Recipients > Groups, locate the group with the users licensed to use CodeTwo by clicking an appropriate tab (e.g. Distribution list) and click the group name.
In the pane that opens, select the Members tab and click View all and manage members (Fig. 5.).

Fig. 5. Accessing the group membership settings.

Click Add members and add shared mailbox(es) by using the picker.
When ready, click Add. The changes to the group membership will be saved.

Important

It may take some time (up to several hours) for this change to synchronize with CodeTwo. Newly added users (including shared mailboxes) might not get signatures until the synchronization process is complete.

Include a shared mailbox in CodeTwo's Exchange transport rule (cloud signatures only)

This step is required if you use CodeTwo cloud (server-side) signatures with shared mailboxes.

When you use CodeTwo in the cloud or combo signature mode, you need to configure Exchange Online connectors and a transport rule in CodeTwo Admin Panel to specify users (mailboxes) whose emails are to be routed through CodeTwo's service to get signatures. You can either select all users in your Microsoft 365 tenant or limit this scope to users belonging to a selected group (a distribution list or any mail-enabled group), as shown in Fig. 6. Learn more about this scope

Fig. 6. Selecting users whose emails should go through CodeTwo to get cloud email signatures.

If you've limited the scope of licensed users to a selected group, as shown in Fig. 6., be sure your shared mailboxes are added as members of this group, as described here.

Enable message copying to the Sent Items folder of a shared mailbox

This step is required if you want to use the Sent Items Update (SIU) feature with CodeTwo cloud (server-side) signatures.

If message copying is enabled for your Microsoft 365 shared mailbox, the copy of all emails sent from that mailbox (either as on behalf of that mailbox by other users) will also be saved in the Sent Items folder of that mailbox. This allows CodeTwo's Sent Items Update (SIU) service to add signatures to emails in the shared mailbox’s Sent Items folder.

To configure message copying in Microsoft 365, you need to:

Connect to Exchange Online, as explained in this article.
Run the following cmdlets to allow Exchange Online to copy emails sent by delegates with either type of delegate permissions:
```
Set-Mailbox <shared-mailbox-email-address> -MessageCopyForSentAsEnabled $true
Set-Mailbox <shared-mailbox-email-address> -MessageCopyForSendOnBehalfEnabled $true
```
Replace <shared-mailbox-email-address> in each cmdlet with the exact email address of your shared mailbox.
Finally, disconnect Exchange Online by running this cmdlet:
```
Disconnect-ExchangeOnline
```

Which Sent Items folder is updated by CodeTwo?

If a user sends an email as a shared mailbox, SIU will only update the copy of that email in the Sent Items folder of the shared mailbox (Fig. 7.). The original email in the user's Sent Items will not be updated with any signature.

Fig. 7. Send as rights: SIU updates emails in the Sent Items of a shared mailbox.

If a user sends an email on behalf of a shared mailbox, SIU will only update the original email in the Sent Items folder of the user (Fig. 8.). The email copy in the shared mailbox's Sent Items will not be updated with any signature.

Fig. 8. Send on behalf rights: SIU updates emails in the Sent Items of the sender.

Important

Note that an email sent on behalf of a shared mailbox accessed through the Open another mailbox feature in Outlook on the web (OWA) won’t be copied to the sender’s mailbox by Exchange Online, which prevents the SIU service from updating the email in the delegate's Sent Items folder. To avoid it, as a delegated user, always send emails from the shared mailbox by selecting it in the email's From field (after clicking Other email address, as shown in Fig. 9.).

Fig. 9. Sending an email on behalf of a shared mailbox in OWA.