How to add signatures to Office 365 shared or resource mailboxes
You would like to add email signatures to shared or resource mailboxes in Office 365.
CodeTwo Email Signatures for Office 365 supports Office 365 shared mailboxes. It is also possible to add a server-side signature to messages manually sent as a resource mailbox. Follow the links below to learn more.
Your shared mailboxes might need to be reconfigured if you want to use all features of the program. Click the links below to learn more.
- Configure a shared mailbox in Microsoft 365 admin center – learn how to configure users' delegate rights (Send As / Send on Behalf) and message copying in Office 365, and how it relates to signatures added by the program.
- Create a dedicated server-side signature for a shared mailbox – find out how to configure the program to add signatures to shared mailboxes and learn when signatures are added.
- Create a dedicated client-side signature for shared mailbox users – find out how to create a client-side signature rule that will provide the users with signatures for use with shared mailboxes.
- Add a client-side signature to an email sent from a shared mailbox – find out how to add your signature when sending an email as a shared mailbox user in Outlook or Outlook on the web (OWA).
When using CodeTwo Email Signatures for Office 365 in combo mode, the solution depends on the email client that is used to send emails from shared mailboxes. Use client-side signatures for messages sent from Outlook and OWA, and server-side signatures for messages sent from other email clients and mobile devices.
Office 365 shared mailboxes need to be correctly configured if you want to use all the features of CodeTwo Email Signatures for Office 365 (including the Sent Items Update service).
- Configure users' delegate rights (Send As / Send on Behalf) to a shared mailbox
- Enable message copying to the Sent Items folder of a shared mailbox
Signatures added to shared mailboxes by the CodeTwo software are based on the sender's delegate rights, as mentioned below.
To assign delegate permissions to users, you need to:
- Log in to the Microsoft 365 admin center.
- Go to Teams & groups > Shared mailboxes from the navigation menu on the left, select the shared mailbox that you want to configure, and click an appropriate link under Manage mailbox permissions (Fig. 1.).
- Depending on the link you've clicked, in a right-hand pane that opens, configure users who can Send as or Send on Behalf of this shared mailbox by clicking Add permissions and choosing appropriate users (Fig. 2.). Depending on these delegate permissions, when users send emails as / on behalf of the shared mailbox, CodeTwo Email Signatures for Office 365 working in server-side mode adds the signature configured for this mailbox / for the original sender. Learn more
This step is required if you want to use Sent Items Update with server-side signature rules. Message copying is not required when using client-side rules. However, you may want to have this feature turned on, depending on company policies related to mailbox use that are set in your organization.
If message copying is enabled for your Office 365 shared mailbox, the messages sent by users with delegate (Send As / Send on Behalf) rights are copied to the Sent Items folder of the shared mailbox. This allows the CodeTwo Sent Items Update (SIU) service to update the Sent Items folder of your shared mailbox with signatures.
To configure message copying in Microsoft 365, you need to:
- Access the settings of your shared mailbox (see steps 1-2 from Configure users' delegate rights...).
- If message copying to Sent Items is disabled (see Fig. 3.), you need to turn it on. Click Edit below Sent Items to open the configuration window.
- Turn on all copying mechanisms and click Save, as shown in Fig. 4.
When message copying is enabled, all emails sent by users as / on behalf of your shared mailbox will be copied to the Sent Items folder of this mailbox. The CodeTwo Sent Items Update service can update these emails with signatures, depending on the senders' delegate permissions:
- If a user sends an email as a shared mailbox, SIU recognizes the email as sent by the shared mailbox and updates only the message copy in the Sent Items folder of the shared mailbox, with the signature defined for this mailbox (Fig. 5.). The original email in the user's Sent Items is not updated with any signature.
- If a user sends an email on behalf of a shared mailbox, SIU identifies this user as the sender and updates only the message in the Sent Items folder of the user, with the signature defined for this user (Fig. 6.). The message copy in the shared mailbox's Sent Items is not updated with any signature.
If you want the program to add a dedicated signature to emails sent from your shared mailbox, you need to:
- Create a new server-side signature rule in the signature management app. Learn more
- On the Senders tab, add your shared mailbox to the list of conditions (by clicking Add > Selected senders and selecting the shared mailbox from the list), as shown in Fig. 7.
- Go to the Design tab and compose a signature for your shared mailbox (Fig. 8.).
- Configure the other rule settings according to your preferences.
- Save all changes.
From now on, depending on the sender's delegate rights (Send As / Send on Behalf), emails sent from this shared mailbox will be stamped with the signature you created for this mailbox or with the signature of the sender:
- If a user sends an email as a shared mailbox (default), CodeTwo Email Signatures for Office 365 recognizes the email as sent by the shared mailbox and adds the signature defined for this mailbox (Fig. 9.).
- If a user sends an email on behalf of a shared mailbox, the CodeTwo software identifies this user as the sender and adds the signature defined for this user (Fig. 10.), according to your rules.
If you want to configure users' delegate rights to your shared mailbox, see this section.
To use client-side signatures when sending emails from a shared mailbox, you must first create a client-side signature rule that will include all users who can send messages from the shared mailbox. To do so:
- Create a new client-side signature rule in the signature management app. Keep in mind that the rule name will be the same as the name of the signature template made available in Outlook. Learn more about creating client-side signature rules
- On the Senders tab, add all users who have been assigned Send As or Send on Behalf permission to your shared mailbox(es) to the list of conditions (by clicking Add > Selected senders and selecting the shared mailbox users from the list), as shown in Fig. 11.
- Go to the Design tab, open the signature template editor by clicking the Edit signature button, and create a signature for your shared mailbox (Fig. 12.). Learn more
- Finally, go to the Options tab and unselect the Set this signature as default for new messages and Set this signature as default for replies and forwards options, as shown in Fig. 13. That way, the signature for shared mailbox will not be inserted automatically if a user uses their default signature more often.
- When done, click the (Save) button (Fig. 14.) to save and submit changes to CodeTwo Azure servers.
Client-side signatures can be automatically added to emails as users type them in Outlook or OWA. However, since you’ve configured the shared mailbox signature as not the default one, your users will need to choose it manually. Follow the steps below to select the signature and send an email as a shared mailbox:
- Click New Email.
- Click From and select Other Email Address from the drop-down list (Fig. 15.).
If the From field is not displayed in the email compose window, go to the Options tab and click the From button on the ribbon.
- In the new window, click From (Fig. 17.).
- Select the shared mailbox address from the contact list displayed in the new window (Fig. 18.) and click OK.
- Click OK twice to return to the email compose window.
- Open the CodeTwo Signatures pane (learn more) and click the Use this signature button next to your shared mailbox signature (Fig. 19.).
If you use the classic CodeTwo Signatures Add-in for Outlook (COM Add-in), you can select your shared mailbox signature manually by using the Signature drop-down on the Outlook’s Message tab. Learn more
- Now that everything’s ready, you can finish composing your message and finally send it from the shared mailbox address (Fig. 20.).
You configured CodeTwo Email Signatures for Office 365 so that only senders belonging to a specific group (or groups) can get email signatures (as explained in the user's manual). You noticed that emails sent as your shared mailbox are not stamped with any signature.
To solve this problem, you need to check if your shared mailbox is added (as a member) to the group whose members get email signatures from CodeTwo. If not, you need to add it. You can do it in the Microsoft 365 admin center (Fig. 21.) or Exchange admin center.
Also, you need to open Exchange admin center and make sure that your shared mailbox is not added as an additional group in the conditions of the CodeTwo Exchange transport rule, as shown in Fig. 22. In the example, the group Users with CodeTwo signatures contains all users who should get email signatures, and the shared mailbox was added directly to the The sender is a member of this group condition. Such a configuration is a common mistake and will not work because shared mailboxes are not treated as group objects in Azure Active Directory. As a result, the condition is not fulfilled.
If your transport rule configuration is similar, you need to:
- Remove your shared mailbox from the The sender is a member of this group condition.
- Add the shared mailbox to a group: it can be the group with users who get email signatures (in the example above, this group is Users with CodeTwo signatures) or you can choose another group or create a new one.
- Add the group that includes your shared mailbox as a member to the conditions of the CodeTwo transport rule.
Emails sent automatically by room and equipment mailboxes do not receive server-side or client-side signatures in CodeTwo Email Signatures for Office 365.
However, it is possible to add a server-side signature to messages manually sent as a resource mailbox. This requires taking an additional configuration step, i.e. adding that mailbox to the All Company group. This will also allow you to select a resource mailbox as a sender in the signature management app and prepare a separate signature for this mailbox if you want to.
If during the configuration of connectors CodeTwo Email Signatures for Office 365 has been set up to add server-side signatures only to messages sent by members of a specific group, your resource mailbox must be added to this group instead. This is done identically as in the case of the All Company group.
If you are using a group other than All Company, remember that it is not possible to add a room mailbox to a Microsoft 365 group. Use a distribution list if possible.
To add a resource mailbox to the All Company group, follow the steps below:
- Log in to the Microsoft 365 admin center.
- Go to Teams & groups > Active teams & users in the left menu, select the All Company group from the list, and click the Members tab (Fig. 23.).
- On the Members tab, click View all and manage members (Fig. 24.).
- Next, click Add members, select the resource mailboxes you want to use and click Add to add the new group members (Fig. 25.). These changes take effect immediately.
At this point, emails sent as any of the selected resource mailboxes will use the signature that is assigned to the group the mailboxes belong to.
By adding resource mailboxes to the All Company group, you make them selectable as senders in the signature management app (on the Senders tab, click Add > Selected senders, as shown in Fig. 26. and discussed in the user’s manual). This means you can now create a separate signature rule and a signature template for resource mailboxes. Learn more
If a resource mailbox is routed through the CodeTwo Email Azure Service to get a signature, it will consume one license identically to any other user in your organization. Further details on licensing are available in the user’s manual.