Send Emails

I need to send an email to some people who have a label, if I schedule it today, it will only be sent even if I schedule it for 3 or 4 days, it will only send to the people who have the label on that day that the sending is created, yes The next day more people enter that same label, it will not be sent to them, how can I send this so that I can schedule the email today, for 3 days from now, as well as send it to all the people who have the label

Create a campaign that starts with the tag (label) you want.
Set a delay timer to run on the day you want the email to go out, then add your email after it.
Anyone who gets that tag added will go into that campaign and wait until that day, and then the email will go out to all people with that tag.