| Release Date |
October 1, 2015 |
October 22, 2018 |
| OS Compatibility |
Windows Server 2012 R2, 2016, 2019 |
Windows Server 2019, 2022 |
| RAM Requirements |
Minimum: 8GB, Recommended: 16GB |
Minimum: 8GB, Recommended: 128GB |
| Processor Requirements |
x64 architecture, Intel/AMD |
x64 architecture, Intel/AMD, AVX support |
| Mailbox Databases per Server |
5 |
5 |
| Max Mailbox Size |
Limited by storage |
Limited by storage |
| Maximum Storage per Database |
16TB (NTFS), 100TB (ReFS) |
16TB (NTFS), 100TB (ReFS) |
| Dynamic Database Cache |
No |
Yes |
| Improved Search Indexing |
No |
Yes (Search indexing moved from dedicated service to local database engine) |
| Calendar Management |
Yes |
Yes |
| SSL/TLS Encryption |
SSL 3.0/TLS 1.0, 1.1, 1.2 |
TLS 1.2 (Only) |
| Client Access Protocols |
MAPI, HTTP, POP, IMAP, EWS |
MAPI, HTTP, POP, IMAP, EWS |
| Unified Messaging |
Yes |
No |
| Storage Optimizations |
Limited |
Improved I/O optimizations |
| Hybrid Configuration |
Yes |
Yes, with enhanced Hybrid Configuration Wizard (HCW) |
| Outlook on the Web (formerly OWA) |
Yes |
Yes, with improved user interface |
| Modern Authentication (OAuth) |
No |
Yes |
| Enhanced Security Features |
Basic Security Features |
Windows Server Core Support, more secure default configuration |
| Container Support |
No |
Yes |
| Public Folder Support |
Yes |
Yes |
| High Availability Improvements |
DAG (Database Availability Group) |
DAG with enhanced failover capabilities |
| Transport Layer Security (TLS) 1.3 |
No |
Supported |
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