CodeTwo Email Signatures for Office 365 is a cloud-based software solution for Office 365 tenants, designed to add email signatures and disclaimers to your Office 365 emails. The signature adding mechanism is based on rules. The software lets Office 365 administrators and authorized users create rules to centrally manage email signatures via an easy-to-use ClickOnce application that is installed locally. It can be launched from your PC or from the program’s website. The main software engine - the CodeTwo Email Azure Service - processes emails on Microsoft Azure servers and adds signatures on the fly. All email clients and mobile devices are supported.

Architecture of CodeTwo Email Signatures for Office 365.
Fig. 1. The program adds signatures to emails sent from any device.

How it works

The software is a cloud-based service that resides in Microsoft datacenters on Microsoft Azure servers. During the initial configuration, our software creates connectors in your Exchange Online organization to reroute all outgoing and internal emails from your Office 365 tenant through the CodeTwo Email Azure Service for processing. When a user sends an email from an Office 365 account (regardless of the email client) as shown in Fig. 2. point 1, this email goes through Office 365 (point 2). The CodeTwo outbound connector redirects the message to the CodeTwo Email Azure Service that checks it against the conditions (rules) configured by an authorized signature administrator in your organization and adds a signature if these conditions are met (point 3). In any case, the email is then sent back (via the CodeTwo inbound connector) to the user's Office 365 tenant (point 4) which delivers it to the final recipient in the usual way (point 5).

ESIG for O365 mail flow
Fig. 2. Mail flow in Office 365 with CodeTwo Email Signatures for Office 365.

Security and performance

Even though CodeTwo Email Signatures for Office 365 reroutes your email via a third-party Microsoft Azure service, it is absolutely secure for your business.

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, is a ClickOnce application installed on a local computer. Before installing, read about the supported platforms and requirements.

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 your Exchange Online connectors. The only thing left to do is install the Manage Signatures App to manage your signature rules. The program 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. To read about the program's components, click here. You can also find out more on the installation and configuration process in this article.

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 WYSIWYG editor to compose perfect signature templates. 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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