Both are proven CUI enclave platforms. PreVeil is usually the cheaper, lighter choice for SMBs: encrypted email and file sharing overlaid on your existing commercial Microsoft 365. Exostar suits contractors already living in prime-contractor ecosystems, with managed Microsoft GCC High options and supply-chain integrations.
How to choose
- Choose PreVeil if: you are CUI Basic, under ~50 CUI users, cost-sensitive, and want to keep commercial M365 untouched
- Choose Exostar if: your primes already require Exostar portals, or you need managed GCC High rather than an overlay
- Choose neither if: you handle ITAR/CUI-Specified at scale — go direct to GCC High with US-persons administration
Heavy CUI workflows may be better served by a ZTNA architecture (Zscaler or Cloudflare FedRAMP editions). The free CMMC planner recommends the right platform from your actual usage.