Attic M365 FREE vs GreatHorn Mailbox Intelligence: Side-by-Side Comparison (2026)

Startup and SMB security teams protecting Microsoft 365 will benefit most from Attic M365 FREE because it stops AiTM phishing attacks that bypass MFA, the attack class traditional email filters miss entirely. The tool deploys in five minutes with no payment required, making it immediately useful for resource-constrained teams, and its real-time detection of fake login pages covers both NIST PR.AA and DE.CM functions simultaneously. Skip this if your organization needs protection beyond Microsoft 365 or runs a heterogeneous SaaS stack; Attic is deliberately focused on one platform and one threat vector. Teams running Microsoft 365 or Google Workspace who need users to actually catch phishing will find GreatHorn Mailbox Intelligence worthwhile, because the visual sender indicators and on-click URL analysis force friction into the attack chain where it matters most. The tool scores across all three NIST Detect and Awareness categories, with particular strength in DE.CM continuous monitoring and real-time risk assessment that surfaces threats before the user opens them. Skip this if your organization has already deployed a mature endpoint detection layer and expects email security to handle lateral movement detection; GreatHorn prioritizes the user reporting loop and initial threat identification, not forensic analysis of compromise.

Based on our analysis of core features, integrations, company size fit, deployment model, here is our conclusion: