There are several sub signature types. These are outlined below.
All
Used for sub-signatures that will be appended to all emails.
Internal Users
The sub-signature will be appended to all emails when at least one of the recipients is an internal user.
External Users
The sub-signature will be appended to all emails when at least one of the recipients is an external user.
Rule
The sub signature will be applies if the result of a Rule returns TRUE.
C# Script (CMS MSE only)
The sub-signature will be appended to the email if a C# Script returns true.
Member Of Group (Recipients Field)
The sub-signature will be appended to all emails when at least one of the recipients is contained in the group specified.
NOT Member Of Group (Recipients Field)
The sub-signature will be NOT appended to the email when at least one of the recipients is contained in the group specified.
Notes Formula
The sub-signature will be appended to the email if a Notes Formula returns @TRUE.
From version 2.938 and above there is the ability to combine selecting a sub-signature based on lookups and formula Combining Criteria.
Member of Group in Address Book
The sub-signature will be appended to the Signature if the sender is a member of the group listed below.
NOT a Member of Group in Address Book
The sub-signature will be appended to the Signature if the sender is NOT a member of the group listed below.
Member Of Group (SendTo, Copy To, BCCTo Fields)
The sub-signature will be appended to all Signatures if there is a user's email address is a match in the group selected using the SendTo, CopyTo and BlindCopyTo Fields.
NOT Member Of Group (SendTo, Copy To, BCCTo Fields)
The sub-signature will NOT be appended to the Signature if the user email address is a match in the selected group using the SendTo, CopyTo and BlindCopyTo Fields.
Member Of Address Book Group (Recipients Fields)
The sub-signature will be appended to all Signatures if there is a user's email address is a match in the selected address book group selected using the Recipient Fields.
NOT Member Of Address Book Group (Recipients Fields)
The sub-signature will NOT be appended to the Signature if there is a user's email address is a match in the selected address book group using the Recipients Fields.