O365 Admin
How to Set Up Organisation-Wide Email Signatures in M365
Published 27 December 2025
·
7 min read
Organisation-wide email signatures in Microsoft 365 are deployed via Exchange Online mail flow rules, which append HTML signatures server-side to outgoing email. This applies universally regardless of which email client users use.
How server-side signatures work
Server-side signatures have limitations
The Exchange method appends the signature after send - users cannot see it while composing. For rich inline signatures visible while typing, use an Outlook add-in (Exclaimer, CodeTwo). The Exchange method is free and works for basic consistent signatures.
Create a mail flow rule
Exchange admin centre → Mail flow → Rules → + Add a rule → Apply disclaimers
- Name: Org Email Signature - Outbound
- Apply if: Sender is located Inside the organisation
- Do the following: Append the disclaimer
- Fallback action: Wrap
- Priority: 0
Dynamic variables
Available disclaimer variables
%%DisplayName%%
User full name from Entra ID%%Title%%
Job title from user profile%%Email%%
User email address%%Department%%
Department from user profile%%PhoneNumber%%
Office phone number%%CompanyName%%
Company name from tenant settingsKeep user profiles up to date
These variables pull from Entra ID. Ensure users have job title, phone, and department populated for variables to work.
Outlook add-ins as an alternative
For sophisticated signatures with profile photos, banner images, and social links - commercial add-ins are better: Exclaimer, CodeTwo, or Crossware.
Frequently Asked Questions
Q: Can I have different signatures for different departments?
Yes. Create separate mail flow rules with conditions matching by department or group membership. Give each rule a different priority.
Q: Does the Exchange signature work in Outlook mobile?
Yes - because it is applied server-side after sending, it works in all clients.
Q: Can I include a logo image?
Yes but the image must be hosted on a public URL. Link to an image on your website - embedded base64 images are frequently stripped by email clients.