A: You can send as many e-mail campaigns as you like. Your price tier is based on the number of unique contacts that receive an e-mail campaign during the calendar month, not on the number of campaigns or e-mails. A contact who gets five campaigns in the same month counts once. The count starts over on the 1st of each month.
If you have the Marketing Automation add-on, the count also includes contacts who submitted a form or visited your website that month.
You can see your tier in your Billing portal.
If a campaign would take you into a higher tier, you see Tier Upgrade Required when you send or schedule it, with the cost of your current and upcoming tier. Billing administrators, and users who have Can approve increases in price tier of Marketing Automation, click I approve the upgrade and can then send the campaign. Other users click Send request to billing admin and can send the campaign once the upgrade is approved.
With Marketing Automation, if a scheduled campaign or a flow would take you into a higher tier that nobody has approved, it is stopped with the status Missing payment and an upgrade request is sent to your billing administrator.