CodeTwo Email Signatures for Office 365 is a cloud-based software solution for Office 365 organizations. It adds signatures, legal disclaimers and banners to emails sent from any email client and device. Signature adding is based on rules: an Office 365 tenant administrator or delegated users need to design signature templates (or use a wide library of built-in signature templates) and specify when and where these signatures should be added. The software's engine, which operates in the Azure cloud, then checks these conditions and makes sure that the right person always gets the right signature.

How it works

The software is a cloud-based service that resides in Microsoft datacenters on Microsoft Azure servers. CodeTwo Email Signatures for Office 365 can add signatures in three different ways, known as signature modes:

  • In server-side mode (default), your emails are routed through the CodeTwo Email Azure Service (hosted on Microsoft Azure), where they get email signatures. During the process, your emails never leave Microsoft datacenters. This mode works with all email clients and devices. Even though signatures are added after an email is sent, you can see them in the Sent Items folder in Outlook, or you can preview them as you type an email in Outlook, Outlook on the web and Outlook for Mac (a web add-in needs to be deployed first). This mode requires setup of Office 365 connectors - the software can handle that automatically for you.
  • In client-side mode, signatures are available directly in Outlook on a desktop PC and are synchronized automatically with CodeTwo services via an Outlook add-in, so they are always up to date. CodeTwo signatures can be added automatically to new emails, replies and forwards, or you can add them yourself via Outlook's menu. This mode requires installation of CodeTwo Signatures Add-in for Outlook.
  • The combo mode combines both of these modes. An administrator can choose who can use signatures directly in Outlook and who gets signatures server-side (after their email message is sent). If client-side and server-side signatures are both set to apply to all users, then if you send an email using the Outlook desktop app, a signature is added as you type (or can be selected from the Outlook ribbon). If you send an email via any other email client or device, then a signature is added after this message is sent.

Signature mode is selected when you register a tenant to CodeTwo services for the first time, but you can change it at any time. By default, the server-side mode is selected. See this article if you need more information about signature modes.

After you select a signature mode and configure the software accordingly, you need to create signature rules, that is design signatures (or select and customize ready-made templates) and specify who should get them. This is managed via a ClickOnce app called Manage Signatures App, which is installed locally. After you save your signature rules in the app, they will be synchronized to CodeTwo cloud services and users in your Office 365 will start getting signatures right away (as long as they or their emails meet the conditions of these signature rules).

Security and performance

In client-side mode, signatures are available directly in Outlook and are delivered using Office 365 native mechanisms. In addition, client-side signatures fully support messages encrypted with S/MIME or OME (Office 365 Message Encryption).

In server-side or combo mode, CodeTwo Email Signatures for Office 365 reroutes your email via CodeTwo Email Azure Service hosted in Microsoft Azure datacenters. These two modes are absolutely secure for your business because the program:

  • does not accept emails from random mail servers. Only emails received from Office 365 tenants registered with CodeTwo are processed;
  • does not move emails to any third-party servers for processing. The CodeTwo Email Azure Service is installed on Microsoft Azure servers which host Office 365 tenants, so your emails never leave Microsoft's servers;
  • does not store, copy or forward your emails anywhere. Your emails are only routed through our Azure servers for processing and then released back to your original server;
  • does not log any email content or properties other than Message-IDs and time stamps (required for proper monitoring and troubleshooting of the software behavior);
  • does not modify any email content or properties except for:
    • inserting signatures into the email body,
    • adding appropriate Internet email headers (the number of hops registered in headers will rise from x to 2x+1 where x is your usual number of hops, e.g. if normally it is 3, then after deploying CodeTwo Email Signatures for Office 365 it will increase to 7 - this is required by common Internet email exchanging protocols and does not affect the end users at all),
    • adding three header properties (Received, X-CodeTwoProcessed, X-CodeTwo-MessageID) to identify the already processed emails and avoid double stamping of signatures and loop processing;
  • does not modify email senders or recipients. An email processed by CodeTwo Email Signatures for Office 365 looks for recipients (and their email clients and servers) in exactly the same way as emails sent directly from Office 365. No shady-looking domain swaps or sending as / on behalf. Thanks to the Azure's OAuth 2.0 authentication, the program does not store any clients’ credentials;
  • does not delay email delivery by more than a few seconds. In our tests, with average Office 365 standalone email delivery times of around 40 seconds, CodeTwo processing took only around 6 additional seconds;
  • is bottleneck-resistant. As our CodeTwo services are installed in the Microsoft Azure cloud, their processing power is fully scalable;
  • allows the tenant's admin to specify who can manage email signatures in an Office 365 organization.

Learn about data safety on the product's page.


The main engine - CodeTwo Email Azure Service - runs entirely in the cloud. It requires you to have a supported Exchange Online / Office 365 plan and needs your global admin's permission to access your tenant. CodeTwo Admin Panel, used to manage tenant-related settings and subscriptions, is a web-based component - only a web browser is required.

The Manage Signatures App (which lets you create signature rules) and CodeTwo Signatures Add-in for Outlook (which adds signatures to Outlook if the CodeTwo software works in client-side mode) are ClickOnce applications installed on a local computer. Before installing, read about the supported platforms and requirements.

A new, entirely web-based interface with cross-platform signature design and management features will soon be available as well. Learn more

Software installation and initial configuration

Setting the software up is as easy as launching the web-based CodeTwo Admin Panel and going through configuration wizards that will automatically register your Office 365 tenant to the program and configure next steps according to the signature mode you selected. The only thing left to do is install the Manage Signatures App to manage your signature rules. The app is installed locally using Microsoft's ClickOnce deployment method. Such a solution minimizes the software's load on your system and ensures that the program is always up to date. If you want users to have signatures available directly in Outlook (this is possible when the CodeTwo software works in client-side or combo signature mode), they need to install CodeTwo Signatures Add-in for Outlook on their desktops. To read about the program's components, click here. You can also find out more on the installation and configuration process in this article.

Easy and automatic conversion of on-premises email signatures

If you are migrating from an on-premises Exchange to Office 365 and you have been using one of our products from the CodeTwo Exchange Rules family, you can easily transfer all your signature/disclaimer adding rules and custom signature templates directly to CodeTwo Email Signatures for Office 365. Learn more

Signature rule management

A ClickOnce application - the Manage Signatures App - is used to manage signature rules. You can specify when your signatures will be added to emails and use the software's built-in signature template editor with a wide library of templates to compose perfect signatures. Learn more


The software is completely transparent to end users. As the CodeTwo Email Azure Service works in the cloud, the process of adding signatures to emails is invisible and independent of the end users' email clients or actions. Once configured and started, CodeTwo Email Signatures for Office 365 will add signatures to every email sent from Office 365 accounts that meet the conditions defined in your rules. Signatures are added regardless of the email client used: everything works in OWA (Office 365), Outlook and other popular email clients, including their mobile versions.

See next

Frequently Asked Questions
Configuration of the program

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