Relevant Product: Exclaimer Cloud - Signatures for Office 365
Exclaimer Cloud - Signatures for Office 365 licensing is based on the number of active email users in your organisation.
(A user is defined as an individual email address that gets a signature applied.)
You either pay on a monthly basis or yearly basis for licensing.
Note: For more information, see Billing frequency of Exclaimer Cloud - Signatures for Office 365.