StrataMail Email Continuity Setup — Filter-Behind Architecture

StrataMail Email Continuity operates as a failover continuity layer behind your spam filter. The filter is always the primary mail handler. StrataMail Email Continuity is the safety net that catches inbound mail when the customer's primary mail server is unreachable. This article covers per-platform configuration for every supported filter.

The Architecture — StrataMail Behind the Filter

Normal mail flow:

Internet → Spam filter (primary MX) → Customer's mail server

Failover mail flow (when customer mail server is down):

Internet → Spam filter (primary MX) → StrataMail Email Continuity (filter's failover destination)
         → Queue → Customer's mail server (on recovery)

For a full explanation of both StrataMail products, see the StrataMail Email Continuity overview on the Infinity Data Center website.

Configuration A — SpamWeeder Premium Integration (Recommended)

SpamWeeder Premium includes native multi-destination delivery, which automatically routes mail to StrataMail Email Continuity when the primary mail server is unreachable. This is the most seamless configuration and requires no DNS changes.

How it works:

• SpamWeeder Premium is the primary MX for the domain — all inbound mail flows through it
• SpamWeeder's multi-destination delivery is configured with two targets: the customer's primary server (priority 1) and StrataMail Email Continuity (priority 2)
• When SpamWeeder cannot reach the primary server, it automatically routes to StrataMail — no DNS change, no manual intervention
• StrataMail Email Continuity queues the mail and retries delivery to the primary every 5 minutes
• When the primary recovers, StrataMail flushes the queue automatically

Setup steps:

1. Add the domain in the StrataMail portal. Select Both delivery mode if webmail access during outages is needed, or Relay only for queue-and-redeliver only. Enter the customer's primary mail server as the relay host. Enable monitoring.
2. In SpamWeeder admin, navigate to the domain's delivery settings.
3. Add StrataMail Email Continuity as the secondary destination in SpamWeeder's multi-destination delivery configuration.
4. Set StrataMail as the failover target — SpamWeeder will activate it automatically when the primary is unreachable.

Host: mxcont150.mailshelter.com
Port: 25

Learn more: SpamWeeder Premium overview.

Configuration B — Proofpoint Essentials / Enterprise

For customers running Proofpoint, configure StrataMail Email Continuity as the alternate or failover delivery destination for the domain.

Proofpoint Essentials:

1. Log in to the Proofpoint Essentials admin console.
2. Navigate to Company Settings → Inbound → Delivery.
3. Find the domain's mail server configuration.
4. Add StrataMail Email Continuity as a secondary delivery host with a higher cost value than the primary.
5. Proofpoint will attempt the primary first and fall back to StrataMail if the primary is unreachable.

Proofpoint Enterprise:

1. Navigate to Email Protection → Mail Routing → Host Groups.
2. Create or edit the host group for the domain.
3. Add StrataMail Email Continuity as a secondary MX host in the group with a higher priority number.

SMTP host: mxcont150.mailshelter.com
Port:      25
Role:      Secondary / failover destination

Configuration B — Mimecast

1. Log in to the Mimecast Administration Console.
2. Navigate to Administration → Gateway → Policies.
3. Select Routing and find or create the delivery route for the domain.
4. Configure StrataMail Email Continuity as the failover delivery target in the delivery route settings.
5. Set the failover condition to activate when the primary mail server is unreachable.

SMTP host:          mxcont150.mailshelter.com
Port:               25
Failover condition: Primary server connection failure

Configuration B — Barracuda Email Security Gateway

1. Log in to the Barracuda Email Security Gateway admin interface.
2. Navigate to Mail Routing.
3. Find the domain's destination mail server settings.
4. Add StrataMail Email Continuity as a backup destination with a higher cost metric than the primary server.
5. Barracuda will route to the lowest-cost available destination — StrataMail activates automatically when the primary is unreachable.

SMTP host:   mxcont150.mailshelter.com
Port:        25
Cost metric: Higher than primary (e.g. primary = 10, StrataMail = 20)

Configuration B — Microsoft Defender for Office 365 / Exchange Online Protection

For M365 customers using Defender or EOP as their inbound filter, configure an outbound connector to route to StrataMail Email Continuity as the failover destination for on-premises or hybrid Exchange delivery.

1. Log in to the Exchange Admin Center (admin.exchange.microsoft.com).
2. Navigate to Mail flow → Connectors.
3. Create a new connector from Office 365 to your on-premises mail server.
4. In the smart host settings, add both the primary mail server and StrataMail Email Continuity as fallback.
5. For M365 tenant-to-tenant migration scenarios, see the M365 Migration Coverage page for specific guidance.

Configuration C — DNS Secondary MX (No Filter)

For customers who have no spam filter, StrataMail Backup MX Services can be configured as a DNS secondary MX record. This is the last-resort option — it provides queue-and-redeliver protection but no webmail access during outages and no filtering of queued mail.

Add the following DNS record at the domain's DNS provider:

Type:     MX
Name:     @ (domain root)
Value:    mxcont150.mailshelter.com
Priority: 20 or higher (must be higher than the primary MX priority)
TTL:      3600 (1 hour recommended)

In the StrataMail portal, add the domain with Relay only delivery mode. Enter the customer's primary mail server as the relay host and enable monitoring.

Learn more: StrataMail Backup MX Services.

Delivery Mode Selection

When adding a domain in the StrataMail portal, the delivery mode determines what happens to inbound mail during an outage:

Verifying the Configuration

After completing setup, verify the configuration is working before relying on it in production:

1. In the StrataMail portal, temporarily set the relay host for the domain to an unreachable address (e.g. 127.0.0.2).
2. Trigger your filter's failover — in SpamWeeder Premium this is automatic when the relay is unreachable; in other platforms disable the primary delivery route temporarily in your filter's admin.
3. Send a test message to the domain from an external mail account.
4. Go to Continuity → Queue Manager, select the domain, and click Load Queue. The test message should appear.
5. Restore the correct relay host. StrataMail Email Continuity will redeliver the test message within 5 minutes.
6. Check Reports → Uptime & Monitoring to confirm monitoring is active for the domain.

Related Resources

• Getting Started Guide — first-time setup walkthrough
• Monitoring & Alerts Setup — configure email and SMS outage notifications
• StrataMail Email Continuity — product overview
• StrataMail Backup MX Services — queue-and-redeliver product overview
• SpamWeeder Premium — native StrataMail Email Continuity integration
• M365 Migration Coverage — email continuity during tenant-to-tenant migrations