TL;DR
You can't add leads to a campaign that's already running. Lead upload and import are turned off once it's live.
Instead, duplicate the campaign, load only your new leads into the copy, and publish it.
When you import, turn on the option to exclude leads that are already in another campaign, so nobody gets the first email twice.
Don't delete the original campaign or its leads while leads are still mid-sequence. Deleting removes their Master Inbox history.
Only contacts in Active campaigns count toward the 20,000 contacts stored limit. Paused and completed campaigns don't count.
When you'd use this
Use this when a campaign is working and you want to send the same emails to fresh leads, or when your first list is running out.
Step-by-step
Get your new leads. Export a new list from Search (Exclude previously ordered contacts is always on), or prepare a CSV with an "Email" column.
Open the Campaign page (next.listkit.io/campaign).
Click the three-dot menu on the campaign's row and choose Duplicate.
Open the copy with Edit. It opens on step 1, Add Campaign Details. Give it a clear name, like the original name plus "batch 2".
Add only your new leads with Upload CSV or Import from order history. Turn on the option to exclude leads that are already in another campaign, and leave the options to import leads that are unsubscribed or on the global blacklist turned off.
Check the sequence and Campaign Setup, then publish the copy.
Leave the original campaign running until its leads finish their sequence.
Expected outcome
Your new leads get the same sequence in a new campaign, your original campaign keeps its leads, stats and reply history, and nobody receives the first email twice.
FAQ
I want to add more leads to a campaign that is running. How do I do that?
Duplicate it and add only the new leads to the copy, as above. Adding leads to a live campaign isn't supported.
Can I pause the campaign, add leads and resume?
No. Duplicating is the supported way to add leads.
Can I upload lists from other sources?
Yes. Upload a CSV with an "Email" column to the copy.
Will people get the first email twice?
Not if you turn on the option to exclude leads that are already in another campaign when you import.
Should I pause or delete the original campaign?
No. Let it finish. Deleting a campaign or its leads permanently removes their Master Inbox history. Once its leads finish the sequence it no longer counts toward your contacts stored limit, so you don't need to delete it to free space.
Can both campaigns use the same inboxes?
Yes. Campaigns that share inboxes share those inboxes' daily limits.