Mailing Lists
Rebuilding a mailing list
When a list needs rebuilding, what rebuilding does, and why the count can change afterwards.
Last updated September 2, 2026
A list works out its members from your contacts. Rebuild mailing list runs that calculation again, so the list reflects the database as it is now.
When to rebuild
- You have just imported a batch of contacts the list should include.
- You changed the filters and want to see the effect on the count.
- You have retagged or recategorised a set of people.
- The count looks stale next to what you know is in the database.
Rebuilding takes a moment on a large database and tells you while it is working. You can leave the page.
Why the count changed
| Direction | Usual reason |
|---|---|
| Up | New contacts imported or added that match the filters. |
| Down | Unsubscribes and bounces since the last build, or contacts whose tags or categories changed. |
| Down a lot | A filter was edited — check the all/any setting before assuming data was lost. |
REBUILD BEFORE A BIG SEND
It costs a minute and it means the count you approve is the count that goes out.