Why fewer people received the campaign than my list holds

This is normal, and there are four separate filters between "people in the audience" and "people who get the email".

1. Suppressed addresses

Anyone who bounced, complained or unsubscribed is on your Suppressions list and is skipped automatically. On an older list this is often the largest share.

2. Invalid addresses

Addresses that failed validation at import cannot receive mail and are excluded from every campaign. They stay visible on your Contacts page — skipped, not deleted.

3. No marketing consent

Being in a list is not the same as being subscribed. Consent comes from the lead form's consent setting or the customer's store preference, so lists built from ad leads or store syncs frequently contain people who cannot be marketed to.

A routed lead list of 5,000 with a sendable audience of a few hundred is entirely possible and is not a fault.

4. Duplicates across audiences

Sending to several lists and segments at once mails each person once, so overlapping audiences do not add up to the sum of their sizes.

So which number is real?

The audience's Contacts or Members count is how many contacts it holds. The number sent is what survives the four filters above. If the gap is small, nothing is wrong.

When the gap is worth investigating

• A brand-new imported list losing most of its addresses usually means the list was old or bought. Sending to it at scale risks an automatic pause — see Why is my campaign paused?.
• A campaign that reports almost no recipients is more likely a targeting mistake — an empty segment, or an audience whose contacts were removed.

Next: open Suppressions and compare its size against your audience — that is usually where the missing recipients went.