Is there any risk of getting banned by Gmail or other email providers because we are sending a lot of emails and not using an ESP?
To be banned by Gmail or other email providers, you typically need to send the exact same email (same body, same subject) in bulk and in a very short period of time. Pitchbox throttles your outgoing emails and limits the number of daily emails per campaign.
It helps if you personalize your opportunities and set a wider time window for Pitchbox to send emails. In the Outreach Schedule, you get to define that window. The wider the window the longer the wait time between each email.
We have not seen any complaints from customers about getting banned, so as long as you follow the above suggestions you shouldn't have any issues. In addition, we support large-scale email delivery services such as Sendgrid and Mandrill.