This video shows how to quickly and easily deploy an email signature for all users in Office 365 and prevent it from being added to replies and forwards. (the resulting signature is applied on the server level in Exchange Online)
The email signature template has been downloaded from:
https://www.mail-signatures.com/articles/signature-templates/?sts=6630
If you prefer a written article to the video, go to:
https://www.mail-signatures.com/articles/configuring-organization-wide-email-signatures-in-office-365/?sts=6630
For more advanced email signature features, check out CodeTwo Email Signatures for Office 365:
https://www.codetwo.com/email-signatures/?sts=6630