Relevant Products: Signature Manager Outlook Edition
Using Signature Manager Outlook Edition, you wish to treat internal and external email messages differently when applying signatures.
For example, you may want to apply a signature with a sales image and full contact details for external recipients, but no image and only brief details for recipients within your organization.
It is not possible to configure these products to apply signatures based on whether messages are internal or external.
This is because the signature is automatically added as soon as the user chooses to create a new message, or to reply/forward an existing message. At this point, the message has not been sent and/or categorized by Microsoft Exchange as being internal or external.
The only way you could implement this functionality would be by using one of our server side solutions, such as Mail Disclaimers or Signature Manager Exchange Edition (for Microsoft Exchange server). Otherwise, the sender will have to manually define whether or not they want keep or delete the signature applied on each email they send.
Remember that you can create multiple policies with different signatures and allow users to choose between them when composing a message in Outlook. So, you could define separate policies for internal and external emails, new messages and replies, etc.