Mission Critical Email

Zimbra, Office365 and Professional Services for Companies With Mission-Critical Email Needs

Mission Critical Email Is All We Do
Mission Critical Email Is All We Do

More than 120 companies rely on us for their mission-critical Zimbra Licensing, Hosting, Training and Professional Services, and Microsoft 365.

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Zimbra Security Hardening Service
Zimbra Security Hardening Service

Sleep soundly knowing your Zimbra system is better secured! For a fixed fee of $595 we will harden most Zimbra systems to our current security best practices, refined over more than 15 years of work with Zimbra.

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Hardened Zimbra Hosting
Hardened Zimbra Hosting

We host more than 100 email domains for more than 70 global and domestic companies in our hardened Zimbra environment on Amazon Web Services.  Learn why Zimbra themselves asked us to present on AWS Hosting Best Practices at the most recent North American Partners conference.

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Zimbra Professional Services
Zimbra Professional Services

For more than 15 years our Zimbra Professional Services have satisfied scores of Zimbra customers and other Zimbra partners globally. We solve thorny issues including: Life Cycle upgrades and migrations; Disaster Recovery; Security Hardening and Compliance.

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Zimbra Certified Training
Zimbra Certified Training

We are the leading Zimbra Certified Training Partner in the United States, and we supplement Zimbra’s core curriculum with our bespoke Best Practices from more than 15 years of Zimbra Hosting.

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Who We Are

We are the global Zimbra experts with customers in more than 20 states and 10 countries. Our proprietor, Mark Stone, adopted Zimbra for his own company in 2005 and became a Zimbra Partner in 2006. ...
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What We Do

We provide our customers with email systems that are performant, reliable, secure and cost-effective — systems that meet each customer’s Mission Critical Email needs. Zimbra Hosting, Licensing, Training and Professional Services Mission Critical Email is...
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Recent Zimbra Blog Posts

Host Your MTA-STS Text File on Amazon Web Services For Pennies Per Month

Host Your MTA-STS Text File on Amazon Web Services For Pennies Per Month

We know that deploying MTA-STS better secures inbound email and can prevent MITM and downgrade attacks. But you need a public web server to host...
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Zimbra Security Tip – Regulate Outbound Traffic With Stateful Firewalls

Zimbra Security Tip – Regulate Outbound Traffic With Stateful Firewalls

Historically, Zimbra firewalling has focused on regulating only Inbound traffic, but we can better protect our Zimbra systems if we also regulate Outbound traffic by...
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Zimbra Postfix – System-Wide Sender Domain Blocking

Zimbra Postfix – System-Wide Sender Domain Blocking

Sometimes we want to block specific domains from sending email to any of our users.  If you followed the instructions to prevent nested address spoofing,...
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Zimbra Custom Delegated Admin Account – Password Resets Only

Zimbra Custom Delegated Admin Account – Password Resets Only

The Zimbra Network Edition NG module enables a Zimbra Global Admin to create Domain Admins right from the Admin Console. But suppose you want to...
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Secure Your Zimbra Distribution Lists From Bad Actors

Secure Your Zimbra Distribution Lists From Bad Actors

Zimbra's Distribution Lists are widely deployed on account of their powerful productivity-enhancing features, but in a default Zimbra installation, anyone anywhere can send email to any...
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Zimbra Selective Postfix Rate Limiting To Improve Email Deliverability

Zimbra Selective Postfix Rate Limiting To Improve Email Deliverability

In this post, we'll show you how doing selective Postfix rate limiting will improve your Zimbra system's email deliverability. Various trade press accounts have reported...
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How To Defend Zimbra Against Distributed Brute Force Login Attacks

How To Defend Zimbra Against Distributed Brute Force Login Attacks

Increasingly we are seeing distributed brute force login attacks on our Zimbra hosting environment, as well as on our on-premises customers' Zimbra systems. These login...
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Architectural Design Reference for Large Zimbra Deployments in Amazon Web Services

Architectural Design Reference for Large Zimbra Deployments in Amazon Web Services

This post documents a high-level architectural design reference for hosting large Zimbra deployments in Amazon Web Services cost-effectively, with a high degree of security, performance,...
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Zimbra Fail2Ban for Submission Only

Zimbra Fail2Ban for Submission Only

In a previous blog post, I documented how to configure Zimbra's DoSFilter in conjunction with a Failed Lockout Policy with the objective of blocking a...
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Office 365 Address Verification, SPF, DMARC and DKIM

Office 365 Address Verification, SPF, DMARC and DKIM

To date, when most people think of anti-spam, they think of blocking inbound spam. Most people don't think about taking steps to ensure that their...
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