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CLAYTONCYBERNETICS
Email hosting provider

A 100,000‑mailbox, three-region Exchange platform with automatic database failover

An email provider that hired our team to build its in-house Microsoft Exchange infrastructure.

Scale
100,000+ mailboxes, 500+ domains, 250 TB
Engagement
Design, build and operation

The challenge

The provider needed carrier-grade email of its own, with no single point of failure, every patch applied fast and deliverability customers could trust. Mail was its product, so an outage was a product outage for every customer at once.

At this scale, small failures become daily events, so the design assumed they would happen. Database copies on standby servers take over automatically when a primary fails, and three regions mean that no single facility is a single point of failure.

Operations were as important as architecture. Applying every Microsoft patch within four hours of release, authenticating mail with SPF, DKIM and DMARC, and filtering spam in both directions kept the platform both secure and trusted by the receiving servers that decide whether customers' mail is delivered.

What our team delivered

  • Redundant dedicated colocation in three regions, 250 TB of iSCSI storage and virtualized servers
  • Exchange database availability groups with copies in more than one region, so a server or a site can fail without users losing mail access
  • Automatic database failover to standby copies for near-zero downtime for every user
  • Postfix, Active Directory, Microsoft 365 and Exchange 2019 through Exchange Server Subscription Edition
  • Every Microsoft patch applied within 4 hours of release, through a staged process that kept copies in service during updates
  • SPF, DKIM, DMARC and TLS encryption on inbound and outbound mail; custom inbound and outbound spam filters
  • Custom monitoring agents with an in-house algorithm that watches message patterns
  • Autodiscover for 500+ domains; certbot integration and scripts that renew SSL certificates automatically
  • Custom APIs integrating e-commerce and the messaging infrastructure

Result

Carrier-grade email for 500+ domains with no single point of failure. The same architecture, at a smaller scale, now protects the email of the conglomerate, PR agency and consultancy described on this page, and it is the basis of our Exchange and Active Directory practice.

Mail that keeps flowing

Incoming mail is authenticated and scanned before it reaches anyone, mailboxes are copied across three regions so a server failure goes unnoticed, and outgoing mail leaves signed and encrypted.

Mail that keeps flowingDiagram of enterprise email flow. Inbound mail from an internet sender reaches the MX edge server running Postfix, where SPF, DKIM and DMARC checks light up in sequence, then passes a spam and malware filter; a spam message is diverted to quarantine. Clean mail is delivered to a mailbox cluster, a database availability group with copies in three regions. On a loop the active server in region A fails and the copy in region B activates automatically, so the next message is still delivered. Outbound mail from the user's mailbox is DKIM-signed and sent over an encrypted TLS connection to the recipient. INBOUNDOUTBOUNDSenderInternetMX edgePostfixSPFDKIMDMARCThreat filterSpam · malwareQuarantineMAILBOX CLUSTER · DAGRegion ARegion BRegion CActiveCopyActiveCopyMailboxUser inboxDKIM signingTLS encryptedRecipientSPFDKIMDMARCSPFDKIMDMARCOffline

DMARC: from watching to rejecting

Share of mail claiming the domain that passes DMARC (SPF or DKIM aligned), week by week. In the monitoring phase (p=none) reports reveal forgotten senders; each one gets SPF and DKIM fixed. Quarantine sends failures to spam, reject refuses them at the receiving server. Illustrative figures.

DMARC: from watching to rejectingLine chart over 12 weeks. DMARC pass rate climbs from 61 percent in week 1 to 78 percent at the end of the p=none phase, 94 percent at the end of p=quarantine, and 99.1 percent in week 12 under p=reject.DMARC pass rate, 12 weeksp=nonemonitor onlyp=quarantinefailures to spamp=rejectfailures refused50%60%70%80%90%100%W1W2W3W4W5W6W7W8W9W10W11W1261%78%94%99.1%Week number on the x axis. Pass rate is measured on aggregate (rua) reports.

Twelve months of availability

Measured availability per site over twelve months against a 99.99% target, which allows 52.6 minutes of downtime a year. Six of seven sites meet it; Singapore misses and is shown in red. Illustrative figures.

Twelve months of availabilityDot plot of twelve-month availability. Miami 99.998, Frankfurt 99.997, New York 99.995, London 99.993, Tokyo 99.992, São Paulo 99.991, all at or above the 99.99 percent target. Singapore 99.987 is below target.Availability per site, last 12 monthsMeets 99.99% targetBelow target99.99% target99.98%99.985%99.990%99.995%100.00%Miami99.998% · 10.5 min downNew York99.995% · 26.3 min downFrankfurt99.997% · 15.8 min downLondon99.993% · 36.8 min downTokyo99.992% · 42.1 min downSão Paulo99.991% · 47.3 min downSingapore99.987% · 68.4 min down · below target

All case studies

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Frequently asked questions

Direct answers to the questions we hear most. Something else on your mind?

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How does the platform avoid downtime?

It uses redundant dedicated colocation in three regions, with 250 TB of iSCSI storage and virtualized servers. Databases fail over automatically to standby copies, giving near-zero downtime for every user. Every Microsoft patch is applied within 4 hours of release.

How is deliverability protected?

SPF, DKIM, DMARC and TLS encryption are used on inbound and outbound mail, with custom inbound and outbound spam filters. Custom monitoring agents use an in-house algorithm that watches message patterns.

How are 500+ domains managed?

Autodiscover covers more than 500 domains, and certbot integration plus scripts renew SSL certificates automatically. The platform runs Postfix, Active Directory, Microsoft 365 and Exchange 2019 through Exchange Server Subscription Edition, with custom APIs linking e-commerce and the messaging infrastructure.

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