Preflight Checks: Validate Your Campaign Before Sending

Preflight validates your campaign before you send or schedule it — checking sender verification, audience, content, links, and workspace send allowance.

Preflight is a validation step that runs automatically when you attempt to send or schedule a campaign. It checks that everything required for a successful delivery is in place. Some issues block sending entirely; others surface as warnings that you should review but that do not stop the send.

What preflight checks

Verified sender

The sender email address on your campaign must be verified in your workspace. Unverified senders cannot be used for delivery. Verify your sending domains and addresses in Settings → Senders.

Blocking: Yes — an unverified sender prevents the campaign from being sent.

Audience selected

Your campaign must have a recipient audience or segment chosen. A campaign without recipients cannot be delivered.

Blocking: Yes.

Subject line

The subject line must not be empty. An email with no subject line is likely to be filtered or ignored.

Blocking: Yes.

Body content

The campaign body must not be empty. A campaign with no content cannot be sent.

Blocking: Yes.

Footer

Every outgoing campaign must contain an unsubscribe link and your business address. SendWhale adds these automatically to the footer — preflight confirms they are present.

Blocking: Yes if missing.

Links

Preflight scans the links in your campaign for obvious issues — for example, blank href values or malformed URLs. Fix any broken links before sending.

Blocking: Warning — link issues are flagged for review but may not block sending depending on severity.

Images

Preflight checks that images referenced in your campaign are loading correctly. Images that return errors will appear as broken in recipients’ inboxes.

Blocking: Warning — image issues are flagged for review.

Workspace send allowance

Your workspace must have sufficient send credits or be within your plan’s sending limits to deliver the campaign. If you are at or over your limit, the send is blocked.

Blocking: Yes if over limit.

Consent and suppression

Suppressed, unsubscribed, and bounced contacts in your selected audience are automatically excluded before delivery. Preflight confirms this suppression check is in place — no action is required from you.

Blocking: Not a blocking issue; exclusion is handled automatically.

Fixing preflight issues

When preflight surfaces an issue, it links directly to the setting or section you need to fix. Resolve each blocking issue before attempting to send again. Address warnings even if they do not block the send — they indicate potential delivery or rendering problems.

1. Review the preflight report

   Read each flagged item and note whether it is blocking or a warning.

2. Fix blocking issues first

   Resolve any issues marked as blocking — these prevent the campaign from being sent at all.

3. Address warnings

   Review and fix warnings where possible before proceeding.

4. Re-run preflight

   After making changes, return to the send or schedule flow to re-run preflight and confirm all blocking issues are resolved.

Passing preflight means SendWhale has accepted your campaign for delivery and all required fields are present. It does not guarantee inbox placement — factors such as your sender reputation, content, and recipient engagement also affect deliverability.