Hard Bounce, Soft Bounce and Safe Email Retry Decisions

Why it matters: A confirmed nonexistent mailbox should generally be suppressed. A temporary rejection may be retried with a delay and a clear attempt limit. Authentication or sender-configuration failures require configuration repair. Use structured provider information where available; a generic SMTP error message is not enough to decide that every recipient is invalid.

• Keep permanent, temporary and configuration errors separate.
• Preserve the provider's diagnostic category.
• Avoid rapid repeated attempts.

Why it matters: If a connection breaks after submission, the provider may have accepted the message even though the application did not receive the response. Automatically resending can create duplicates. Record the attempt and provider identifier when possible, reconcile events, and use provider-supported idempotency where available. Do not pretend an uncertain outcome is a definite failure.

• Track each recipient attempt durably.
• Keep uncertain outcomes out of blind replay.
• Reconcile delivery events before resending.

Why it matters: A campaign-level Retry button should explain which recipients will be attempted again. Successful and suppressed recipients should remain excluded. Cancellation must stop new attempts without rewriting completed history. Clear counts for accepted, failed, skipped and uncertain recipients let users understand what actually happened rather than guessing from a progress bar.

• Preview retry recipients.
• Keep cancellation and failure separate.
• Retain the original failure reason for audit.