Cleaning Up a Microsoft 365 Tenant for a Fire Protection & Security Company

The Challenge

Capital Fire & Security runs its dispatch, service, projects, monitoring, and accounting workflows through Microsoft 365 shared mailboxes and distribution lists. Over years of staff changes, the tenant had drifted: former employees still sat in distribution groups, an external account had ended up in a password-reset group, mail forwarding rules had piled up, and one long-serving staff mailbox had grown to more than 82,000 items.

What We Did

• Produced a complete distribution-list membership report covering every Microsoft 365 group in the tenant, flagging former employees still receiving company mail, an external account inside a self-service password reset group, and inconsistencies between the group structure and how the business actually routes work.
• Executed the approved cleanup: removed departed staff from groups, corrected group memberships for current staff, and restructured service-to-office mail forwarding so tickets land where the team actually works them.
• Handled ongoing joiner/leaver work — new employee mailboxes, password resets, and departed-employee mail handling — with the client’s approval at each step.
• Diagnosed a tricky duplicate-recipient problem on outgoing invoices down to its real cause: legacy client-side Outlook rules on a shared workstation profile, not the server — saving the client from chasing the wrong fix.
• Rebuilt an overloaded staff mailbox using a secure, automated Microsoft Graph API process (no password changes, no user downtime): applied an 18-month retention cutoff approved by management, removed 51,422 old messages, and took the mailbox from 82,456 items to 31,095 — a 62% reduction — then delivered a one-page report documenting exactly what was done.

The Result