StrataMail Email Continuity is a failover email continuity service that sits behind your existing spam filter. It is not a spam filter itself and is not the primary MX for any domain. When your customer's primary mail server becomes unreachable, StrataMail Email Continuity accepts all inbound mail from the spam filter, stores it, and redelivers it automatically when the primary server recovers.
How StrataMail Works — Architecture Overview
The correct mail flow always has the spam filter as primary MX. StrataMail Email Continuity is the failover destination configured inside the filter — not in DNS.
| Step | What Happens | Who Handles It |
|---|---|---|
| 1 | Inbound mail arrives from the internet | Spam filter (SpamWeeder, Proofpoint, Mimecast, etc.) — primary MX |
| 2 | Filter processes the message | Spam filter — scans, scores, blocks or passes |
| 3 | Clean mail delivered to customer primary server | Spam filter → customer mail server (M365, Exchange, cPanel, etc.) |
| 4 | Customer primary server goes down | Spam filter detects failure and activates its failover / alternate delivery |
| 5 | Filter routes to StrataMail Email Continuity | StrataMail Email Continuity receives, stores, and queues the message |
| 6 | Customer primary recovers | StrataMail relay queue flushes — all mail delivered automatically |
Important: StrataMail Email Continuity should never be configured as the primary or only MX record for a domain. It is a continuity failover destination, not a mail relay or filter. Always configure it as the failover target inside your spam filter — not in DNS.
Delivery Configurations
StrataMail Email Continuity supports three delivery configurations depending on the customer's filtering setup:
| Configuration | Filter | How StrataMail Receives Mail | Best For |
|---|---|---|---|
| A — SpamWeeder + StrataMail | SpamWeeder Premium | SpamWeeder's native multi-destination delivery automatically routes to StrataMail Email Continuity when primary is unreachable. No DNS MX change needed. | New customers, customers standardizing on a full inbound stack |
| B — Customer filter + StrataMail | Proofpoint, Mimecast, Barracuda, Defender, or other | Customer's filter is configured to use StrataMail Email Continuity as its alternate delivery destination. The filter handles the failover trigger. | Customers with existing enterprise filtering investment |
| C — DNS secondary MX only | None | StrataMail Email Continuity is configured as a lower-priority MX record. Sending servers fall back to it only if the primary MX is unreachable. | Customers without a spam filter. Queue-and-redeliver only — no webmail access during outage. |
Recommendation: Configuration A (SpamWeeder Premium) is the recommended default. It provides the most seamless failover with no DNS changes and includes webmail access during outages. Configuration C provides queue protection only — no webmail access and no filtering during the outage window.
Not sure which configuration is right for your situation? See the StrataMail Email Continuity overview on the Infinity Data Center website.
What You Will Need
- Your StrataMail admin login credentials (provided by Webservio on account activation)
- The hostname or IP address of the customer's primary mail server (relay host)
- Access to configure your spam filter's failover or alternate delivery settings
- The domain name to protect
Step 1 — Log In
Navigate to your StrataMail portal and log in with your admin credentials. You will land on the Dashboard, which shows the current status of all domains under your account and any active outage events.
Screenshot: Dashboard showing domain list and status indicators — available after first domain is added.
Step 2 — Add the Domain
Click Continuity → Add Domain in the top navigation. Fill in the following fields:
- Domain name — enter the domain to protect, e.g.
customer.com - Delivery mode — select Relay only for Config A and B when webmail access during outages is not needed. Select Both (local + relay) to enable users to read and reply via webmail during an outage — requires a spam filter configured for failover (Config A or B).
- Relay host — the hostname or IP of the customer's primary mail server. This is where StrataMail Email Continuity forwards queued mail when the primary recovers.
- Monitoring — enable to receive alerts when StrataMail cannot reach the relay host.
- Alert email addresses — enter one or more addresses for outage notifications.
Click Add Domain to save.
Delivery mode note: Both mode creates a local shadow mailbox for every message received during an outage. This is what enables users to log into Roundcube webmail and read their mail while the primary server is down. Relay only mode queues mail for redeliver without local storage — no webmail access during the outage.
Step 3 — Configure Your Filter Failover
This step tells your spam filter to route to StrataMail Email Continuity when the customer's primary server is unreachable. The configuration location varies by platform:
| Filter Platform | Where to Configure | What to Set |
|---|---|---|
| SpamWeeder Premium | Multi-destination delivery settings in SpamWeeder admin | Add StrataMail server as secondary destination. SpamWeeder activates it automatically on primary failure. No DNS change needed. |
| Proofpoint Essentials / Enterprise | Delivery settings → Smart host / Alternate route | Add StrataMail SMTP host as failover relay for the domain |
| Mimecast | Administration → Gateway → Policies → Delivery route | Configure StrataMail Email Continuity as the failover delivery route |
| Barracuda Email Security Gateway | Mail routing → Destination mail server settings | Add StrataMail as a backup destination with higher cost metric |
| Microsoft Defender / EOP | Exchange Admin Center → Mail flow → Connectors | Create an outbound connector to StrataMail Email Continuity as failover for on-premises or tenant delivery |
StrataMail SMTP Relay Host
Host: mxcont150.mailshelter.com Port: 25
Config C — DNS secondary MX (no filter): If the customer has no spam filter, add a DNS MX record pointing to StrataMail Email Continuity with a higher priority number than the primary MX. This provides queue-and-redeliver protection only — no webmail access during the outage and no spam filtering of queued mail.
Config C — DNS MX Record
Type: MX Name: @ (domain root) Value: mxcont150.mailshelter.com Priority: 20 or higher (must be higher than primary MX priority) TTL: 3600
Step 4 — Test the Failover
Verify the setup without causing a real outage:
- In the StrataMail portal, temporarily change the relay host for the domain to an unreachable address (e.g.
127.0.0.2) and save. - Trigger your filter's failover — in SpamWeeder this happens automatically when the primary is unreachable; in other platforms you may need to disable the primary delivery route temporarily in your filter's admin console.
- Send a test message to the domain from an external account.
- Go to Continuity → Queue Manager, select the domain, and click Load Queue. The test message should appear queued.
- Restore the real relay host. StrataMail Email Continuity will redeliver the test message within 5 minutes.
Important: Always restore the real relay host after testing. A permanently incorrect relay host will cause all inbound mail to queue indefinitely and never deliver to the primary server.
Related Resources
- StrataMail Backup MX Services — queue-and-redeliver protection overview
- StrataMail Email Continuity — full continuity with shadow mailbox and webmail access
- SpamWeeder Premium — native StrataMail Email Continuity integration, no DNS change needed
- Filter-Behind Architecture Setup Guide — detailed per-filter configuration instructions
- Monitoring & Alerts Setup — configure email and SMS outage notifications
Need help setting up StrataMail Email Continuity? The Webservio engineering team is available to assist with configuration and onboarding.
866.790.4678 — Contact Form
866.790.4678 — Contact Form