InMail credits are a pooled resource shared by all seats on a LinkedIn Recruiter contract. InMail Allocation allows Recruiter admins to set limits on the volume of InMail credits that can be used by seats on a contract level. It also gives admins the control to restrict the ability for seats to send bulk InMail messages.
InMail Allocation is only available for Recruiter Corporate or Recruiter Professional Services (RPS) contracts. InMail Allocation limits can only be placed on Recruiter seat types, not Hiring Manager, Talent Pipeline, or Dashboard Manager seats.