If you have not connected a Google or Office 365 inbox in HubSpot, you can send up to 500 emails per user per day when sending from the CRM.
If you have connected your Google or Office 365 inbox, there is no limit on the number of emails that can be sent from the CRM. The number of emails sent through the CRM does not count toward your email limit in the HubSpot Marketing product.
If you have the Gmail integration enabled, emails sent from the CRM will be delivered via your Gmail account. Gmail does impose limits on the number of recipients that are sent emails on your behalf through another service on a daily basis. This limit is 50% of their overall daily sending limits.
- Free users are limited to ~250 recipients/day.
- G Suite (formerly known as Google Apps for Work) users are limited to ~1000 recipients/day.
Here is Google's documentation on these limits. If you do hit this limit, Gmail will notify you and the number of emails sent will reset in about 24 hours.