CodeTwo Email Signatures 365 is a cloud-based software solution for Microsoft 365 (Office 365) organizations. It adds signatures, legal disclaimers and banners to emails sent from any email client and device, and can be also used to send smart, personalized automatic replies.

Essentially, the operating principle of CodeTwo Email Signatures 365 is based on user-defined rules: a Microsoft 365 tenant admin or delegated users can e.g. design signature templates (or use built-in templates) and specify when they should be added to emails. The software's engine, which resides in the Azure cloud, checks conditions and makes sure that the right person always gets the right signature or has their auto reply sent. CodeTwo Email Signatures 365 offers an all-web experience and can be managed from any device and platform, including Windows and Mac computers, mobile phones and tablets.

How it works

The software is a cloud-based service that resides in Microsoft datacenters on Microsoft Azure servers. Email signatures can be added in three different ways, known as signature modes:

  • Server-side (default): a signature is added after an email is sent and passes through the CodeTwo Email Azure Service. This mode works with all email clients and devices, including mobile phones.
  • Client-side: a signature is added when a user types an email in Outlook. A signature can be added automatically to new emails, replies and forwards, or you can select one manually in Outlook.
  • Combo mode: an email sent from Outlook gets a signature when you compose a message; an email sent using another email client (e.g. a mobile mail app) gets a signature after it 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. The server-side mode is selected as default so that the process of adding signatures is invisible and independent of end users' email clients or actions. See this article if you need more information about signature modes.

Signatures are managed using signature rules: for each rule, you design a signature and specify who should get it, and when. Signature rules are synchronized to CodeTwo cloud services so that all users in your Microsoft 365 tenant get the right signatures.

Security and performance

In client-side mode, signatures are added to emails directly in Outlook and OWA by a dedicated signature add-in which is deployed centrally by an admin to selected users. The add-in can access basic user information only (this is needed to add the right signature). All communication between the add-in and CodeTwo services is encrypted and secured using native security mechanisms available in Microsoft 365. 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 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 Microsoft 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 Microsoft 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 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 365 looks for recipients (and their email clients and servers) in exactly the same way as emails sent directly from Microsoft 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 Microsoft 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 a Microsoft 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 / Microsoft 365 plan and needs your global admin's permission to access your tenant.

Tenant settings and signatures are managed on the web, so only a web browser is required.

Optional components (such as Outlook add-ins) might require, for example, specific versions of Outlook. Before installing, check the supported platforms and requirements.

Architecture and components

Application interface components

These components are managed by the customer.

  • CodeTwo Admin Panel - a web interface that lets you control settings of the registered tenant(s), access signature management, control access rights to email signature rules, purchase a subscription, change your payment method or check the status of CodeTwo services. Learn more
  • Signature management app - a web interface used to manage signature rules and create signature templates via the built-in signature template editor. It's also used to create and manage automatic replies. The interface be accessed by authorized users only, either directly at app.codetwo.com or via the CodeTwo Admin Panel. Learn more
  • Outlook add-ins that allow users to add client-side signatures in Outlook while composing messages. There are two signatures add-ins, but you can use either of them:
    • New experience: modern CodeTwo Signatures Web Add-in for Outlook and OWA - co-engineered with Microsoft, this add-in adds signatures to emails in Outlook for Windows, Outlook for Mac & Outlook on the web / OWA. It can also be used to preview server-side signatures (added in the cloud after an email is sent). The add-in is deployed from the Microsoft 365 admin center (you can get in from Microsoft AppSource) to selected Outlook users; no need to install anything locally.
    • Classic experience: CodeTwo Signatures Add-in for Outlook (COM Add-in) - this add-in adds signatures to emails in Outlook for Windows only. You can deploy it to your organization via GPO or Microsoft Intune, or ask users to download and install it themselves.

      Learn more about the differences between the two Outlook add-ins
  • User attributes manager - a web interface used to bulk edit all user attributes stored in CodeTwo Azure AD cache and create custom attributes. Learn more
  • User info editor - a web interface that allows end users to edit their own attributes (made available for them in the User attributes manager). Learn more


The application's services are installed on Microsoft Azure servers and are handled by CodeTwo. All the services use TLS (Transport Layer Security) 1.2 to provide maximum safety and meet all Microsoft standards.

  • CodeTwo Email Azure Service - the main engine of the software, deployed to Microsoft Azure servers. It's responsible for the processing of your rules and adding signatures to your emails. It also stores your tenant's settings.
  • Azure AD cache - another CodeTwo service installed in Microsoft's datacenters. The Azure AD cache holds a local copy of your Azure Active Directory properties to allow for instant resolving of AD placeholders without the need to constantly query your Active Directory. The service synchronizes this cache with the actual AD every 20 minutes. Learn more
  • Sent Items Update (SIU) - this service is responsible for updating email copies in the Sent Items folder with the signatures that were added (by the program) to outgoing emails. By default, the SIU service is disabled and needs to be enabled in the CodeTwo Admin Panel. Learn more
  • Autoresponder - the service allows you to create and send customizable auto-reply messages for selected users or groups in your organization. To use this feature, you need to enable it in the CodeTwo Admin Panel. Learn more

Deployment and initial configuration

To configure the service, you need to launch the web-based CodeTwo Admin Panel and go through configuration wizards that will automatically register your Microsoft 365 tenant to the service and guide you through the next steps according to the signature mode you selected.

Email signatures are managed via a web browser at app.codetwo.com

If you want users to have signatures available directly in Outlook (this is possible when the CodeTwo service works in client-side or combo signature mode), you need to deploy signatures add-in for Outlook first.

Learn more about the program's deployment and configuration process

Easy and automatic conversion of on-premises email signatures

If you are migrating from an on-premises Exchange to Microsoft 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 365. Learn more

Signature rule management

You can specify which users will get email signatures or which signature template should be added to which messages by creating signature rules. Rules are managed using a web-based interface, accessed at app.codetwo.com. The software's built-in signature template editor comes with a wide library of templates that you can use to compose perfect signatures. Learn more

Autoresponder rule management

Apart from signature rules, CodeTwo Email Signatures 365 allows you to create autoresponder rules where you can define users for whom smart auto replies (out of office messages) will be sent and recipients who will get them (if the conditions you specify are met). An auto reply content can be freely customized – you can add links, graphics, personalized email signatures, and more. Select one of pre-defined auto-reply templates or create your own from scratch. To manage autoresponder rules, you first need to enable Autoresponder in CodeTwo Admin Panel. Learn more

See next

Frequently Asked Questions
Get started with CodeTwo Email Signatures 365 (deployment and configuration)

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