Queue and Send Strategy

The send strategy defines how work enters the queue. The queue shows what the SMTP engine is doing now.

Configure the global strategy

Open Settings → Send Strategy and review the fields supported by your version:

• global send rate;
• allowed sending window;
• retry count or delay;
• automatic throttling;
• other provider- or account-level defaults.

Start conservatively. Use limits documented by the infrastructure provider and adjust based on real delivery evidence. Campaign-specific settings should be exceptions with a recorded purpose.

Monitor the queue

The queue view exposes:

• queued, active, completed, and failed work;
• current throughput;
• SMTP response entries;
• sender- and domain-level throttling;
• recent errors and backlog.

Filter or inspect logs around the time and campaign of an anomaly. Do not infer the cause from one metric alone.

Queue controls

• Pause queue: stop scheduling new queue work while retaining state.
• Resume queue: continue after the cause has been reviewed.
• Stop all sending: end active sending across campaigns; confirm the displayed affected count and use it for an incident or intentional shutdown.
• Automatic throttle: allow the engine to reduce rate in response to supported signals.

A paused campaign and a paused global queue have different scope. Check both when work does not resume.

Respond to warning signals

Pause and investigate when:

• hard-bounce or complaint rate rises unexpectedly;
• one recipient domain shows repeated deferrals;
• an SMTP account begins authentication failures;
• the queue grows while throughput falls;
• unsubscribe or hosted service health degrades;
• DNS authentication changes unexpectedly.

Correct the root cause before resuming. Repeated retries can worsen recipient-provider pressure and consume account capacity.

Rate changes

Change one variable at a time, use a bounded audience, and observe for enough time to capture delayed bounces. Record the previous value, new value, campaign, and outcome in the operational log.

Next: understand suppressions.