Exchange Server 2016 shipped in October 2015, consolidating the Client Access and Mailbox roles introduced in 2013 into a single Mailbox role, and bringing MAPI/HTTP as the default protocol for Outlook. It reached end of extended support on 14 October 2025 alongside Exchange 2019 — the entire on-premises Exchange line is now succeeded by Exchange Server Subscription Edition (SE), which is the only on-premises Exchange still receiving security updates.
Standard (up to 5 mailbox databases per server — sufficient for small and mid-size deployments) and Enterprise (up to 100 mailbox databases — required for large estates and for hosting more than five public folder databases). Both editions share the same feature set; the difference is purely the database count limit.
Server licence (Standard or Enterprise) plus a CAL for every user or device. CALs come in two flavours: Standard CAL (basic mailbox access, ActiveSync, OWA) and Enterprise CAL (adds in-place hold, advanced compliance, data loss prevention, journaling, integrated archiving). Enterprise CAL is additive — you buy a Standard CAL and add an Enterprise CAL on top, you do not buy Enterprise CAL alone.
Mainstream support ended October 2020; extended support ended 14 October 2025. After that date, no security patches. Migration paths: Exchange Online (Microsoft 365), Exchange Server Subscription Edition (the new on-premises evergreen line), or a hybrid deployment with mailbox moves to Exchange Online over time. Running Exchange 2016 in production after October 2025 with internet-exposed mail flow is a documented and serious security risk.
Relative fit of each licensing channel for typical buyers of this product. Calibrate against your own scale and renewal strategy.
Exchange, SharePoint and Project Server are mature on-prem workloads whose pricing assumes you have already decided not to move to Microsoft 365. Validate that decision honestly before you commit to a multi-year hardware and CAL refresh.
The small set of decisions that determine whether you overpay, fail an audit, or land in the right place.
Three reference deployments — find the closest match and adapt rather than starting from zero.
None of these are tricks — they are the same levers Microsoft's own licensing specialists pull on every renewal.
These four signals show up in every counterfeit-licence case we have seen. If any of them is present, walk away — no discount makes it worthwhile.
OEM keys are distributed only pre-installed on hardware and stay bound to that device for life. A separately sold OEM key is almost certainly leaked, harvested from scrapped hardware, or fully counterfeit.
Microsoft entitlement always leaves a paper trail — a Volume Licensing Service Center record, a CSP invoice, a sealed Retail box with a COA, or a Microsoft Store order. No proof = no defence in an audit.
Classic symptom of a MAK key that has exceeded its activation pool, or a KMS key being abused outside its volume programme. Microsoft revokes these centrally; the activation grace period is short.
Legitimate CSPs and LARs transfer the licence into your Microsoft 365 / Azure / VLSC tenant under your domain. If the seller insists on activating 'for you' on their account, you do not own anything.
Quick definitions — the full glossary lives at /en/glossary if you need to dig deeper.