Microsoft Exchange / O365
My knowledge of all versions of Microsoft Exchange is unrivaled. Be it deployments, migrations, rebuilds, or simply day-to-day support, there is nothing about Exchange that I haven't seen.
Office 365
Office 365 migrations have become a staple skill of any messaging engineer. I've even published a Best-Selling course on migrating from Exchange to O365 using the native tools supplied by Microsoft.
Microsoft Azure
An extremely fun technology to work with. I've architected simple solutions as well as larger and complex HA multi-tier infrastructures. I have also deployed AD-integrated solutions and other complex architectures.
Active Directory
Probably my favorite discipline. I've architected, implemented, and supported Active Directories as large as 40K+ seats and as small as 10 seats. I'm also well-versed in migrations, consolidations, and integrations - even with Azure AD.