Mimecast Decommissioning & Transition
Confidently transition away from Mimecast
Expert guidance that brings clarity, predictability, and reduced risk to your move into Microsoft 365 and modern email security — without disruption or hidden surprises.
Independent specialists with deep industry experience and former Mimecast consultants. We help you understand your current posture, plan the transition, and execute with confidence.
Strategic context
Moving away from Mimecast is a strategic decision, and a complex one.
Many organisations are reviewing their reliance on secure email gateways as they consolidate technology stacks, optimise spend, and take advantage of native Microsoft 365 capabilities that they're licensed to use.
On the surface, it might seem like a relatively simple change, but in practice it's rarely straightforward. Controls behave differently. Policies don't translate neatly. Application relays and legacy routing paths often depend on Mimecast without anyone realising. Email deliverability can be materially affected by changes to Policies, SPF, DKIM, DMARC, MTA-STS, and TLS.
It's a change with meaningful business impact that requires clarity, sequencing, and specialist knowledge to execute correctly.
Customer highlight
A 3,000-seat professional services firm engaged Cydaura to audit Mimecast policies and produce a transition plan for Microsoft 365. Over three weeks, our team identified multiple business applications still routing mail through Mimecast that would have otherwise been missed and would have caused deliverability failures.
We mapped all policies, provided an equivalent Microsoft and complementary vendor structure, and delivered a validated transition plan that ensured continuity and a smooth decommissioning process.
What organisations want from a modernised email security model
Teams transitioning away from Mimecast consistently aim for:
- •A simpler, more consolidated email security architecture.
- •Confidence that Microsoft 365's native controls including Defender for Office 365, Advanced Delivery, anti-spam, DLP, and secure configurations that are aligned with best practices.
- •Clarity on where a complementary vendor may be needed (for example Abnormal, IronScales, Avanan, Tessian/Proofpoint, CheckPoint/Avanan and others).
- •A transition plan that avoids business disruption and email deliverability issues, while maintaining or improving security posture.
- •Predictability over timelines, responsibilities, testing, and handover.
The ideal future state is modern, well-understood, and fit for your organisation's operational and security needs.
What's needed for a safe, predictable transition
When you routinely help organisations working through complex transitions, you build a framework for success.
1. Understand your business & objectives
Our consultants partner with your IT and security teams to build a detailed view of your organisation, goals, and project requirements before anything changes.
2. Review & document Mimecast configuration
We run a detailed review of every Mimecast setting, policy, and definition, building a documented baseline we can workshop with your team to confirm intention, currency, and validity.
3. Configuration & policy mapping
We run a detailed mapping exercise between Mimecast and Office 365, aligning functionality where possible and recommending alternate approaches when a direct translation isn’t available.
4. Transition planning
We deliver a structured plan that shows where coverage improves, stays equal, or needs complementary controls, plus a transition sequence tuned to your organisation.
1. Understand your business & objectives
Our consultants partner with your IT and security teams to build a detailed view of your organisation, goals, and project requirements before anything changes.
2. Review & document Mimecast configuration
We run a detailed review of every Mimecast setting, policy, and definition, building a documented baseline we can workshop with your team to confirm intention, currency, and validity.
3. Configuration & policy mapping
We run a detailed mapping exercise between Mimecast and Office 365, aligning functionality where possible and recommending alternate approaches when a direct translation isn’t available.
4. Transition planning
We deliver a structured plan that shows where coverage improves, stays equal, or needs complementary controls, plus a transition sequence tuned to your organisation.
How Cydaura helps you transition with clarity and confidence
Cydaura is built by former Mimecast consultants with deep technical knowledge of how these platforms behave in practice. Combined with our independent position, we help organisations make the right decisions — free from sales bias.
Our approach focuses on clarity, predictability, and reduced risk across every stage of your transition.
Comprehensive capability & configuration mapping
We conduct a structured review of:
- •Mimecast configuration, policies, routing, and app relays
- •Microsoft 365 and Defender capabilities, including Advanced Delivery and secure defaults
- •Opportunities to consolidate into Microsoft's native features
- •Scenarios where complementary controls add value or close gaps
- •Dependencies that may cause disruption if removed incorrectly
This mapping reveals hidden mail flow dependencies, legacy routing paths, applications still relaying via Mimecast, redundant policies, controls that cannot be replicated like-for-like, gaps and recommended alternatives, plus DNS changes that require careful sequencing.
Considering archive migration as part of decommissioning?
We help make moving your Mimecast Archive Data to Microsoft Office 365 or an alternative solution fast and efficient.
Move Fast
Meet Deadlines
Up to 1TB/Day Data Extraction
Keep data in useable formats
Migrate to anywhere
Export to PST / EML ready for O365
Regain control over your data
Runs in your Azure
Exported to your Azure Blob Storage
Fully managed archive migration
Why organisations choose Cydaura
Industry specialists with deep real-world experience
Every consultant has worked in Mimecast's professional services or technical teams. We know the platform inside out and understand how it behaves in real customer environments.
Independent and vendor-neutral
We don't sell software. We help you make the right security and operational decisions for your organisation, whether that's purely Microsoft, Microsoft plus a complementary vendor, or a staged approach.
Proven methodology, clear communication
From global enterprises to public sector bodies, we've delivered secure, predictable transitions at scale. We bring clarity to complex projects and give your teams confidence at every step.
Industry specialists with deep real-world experience
Every consultant has worked in Mimecast's professional services or technical teams. We know the platform inside out and understand how it behaves in real customer environments.
Start your transition with confidence
If you're planning a move away from Mimecast — or exploring whether now is the right time — we can help you understand the path, avoid risks, and build a future-ready email security model.