Mimecast Email Security Stops Phishing Campaigns Targeting Accounting Firm
99.97% of malicious email blocked before reaching users — including all impersonation attempts. We delivered this outcome for Central London Chartered Accountants (55 users) by combining Mimecast, Email Security, Microsoft 365 into a single strategic engagement.
What Central London Chartered Accountants was facing
A central London accounting firm was receiving increasingly sophisticated phishing emails targeting their finance team — impersonation attacks designed to trick staff into changing client bank details for tax refund payments. Three near-miss incidents in six months had nearly resulted in fraudulent transfers totalling £180,000. Their existing email security (Office 365's built-in protection) was not catching these targeted attacks, and they needed enterprise-grade email security that could detect impersonation, block phishing, and provide continuity during outages — all while meeting ICAEW compliance requirements for email retention and audit trails.
How we solved it
We implemented Mimecast email security as a comprehensive email protection layer in front of Microsoft 365. We configured impersonation protection rules tailored to the firm's executives and finance team — detecting emails that mimicked partner names, domain spoofing, and lookalike domains. We implemented Safe Links and Safe Attachments for real-time URL and attachment scanning, configured a 10-year tamper-proof compliance archive for ICAEW and FCA requirements, and enabled email continuity so the firm could continue sending and receiving email during Microsoft 365 outages. We also deployed Mimecast's phishing simulation training to educate staff on recognising phishing attempts, with monthly simulations and instant training for users who click.
What we delivered
Tools and skills applied
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The accounting & finance expertise and technical capabilities behind this engagement.
Services
Email Security (Mimecast)
Enterprise-grade email security with Mimecast to stop phishing, ransomware, and business email compromise.
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Sources & further reading
Independent guidance from UK regulators, standards bodies and technology vendors that underpins the advice on this page.
- National Cyber Security CentrePhishing: how to spot and report scamsHow to recognise, report and harden against email-borne attacks.(opens in a new tab)
- MimecastEmail security and resiliencePlatform documentation for the email security service we deploy.(opens in a new tab)
- MicrosoftSecurity threat intelligence and researchVendor threat research and product security guidance.(opens in a new tab)
- National Cyber Security Centre10 Steps to Cyber SecurityThe UK's baseline framework for protecting business systems, people and data.(opens in a new tab)
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