Log into your Office 365 portal – https://login.microsoftonline.com
Click on Admin -> select Exchange
In the Exchange admin center, select Mail Flow and rules
Click on the add symbol and select Apply disclaimers…
In this case, I’m calling this rule Global Signature. Select [Apply to all messages] and Append the disclaimer… We will now enter the text and fall back action.
Insert the text that will appear in the signature. In this case, I entered a carriage return and am using User attributes (see http://help.outlook.com/en-us/140/ff852816.aspx#UserAttributes) to enter the details for each user. Click ok.
Select the fall back action. I chose Wrap. Click ok.
Now click save.
This is how the rules section will look like under mail flow
If you now send a test email from any account, you should see the signature appear in the email.
Hope this helps you!
Thank Sri 🙂