Here is a guide to ensure you have strong deliverability by following the best practices which make sure you do not land in spam,
Checklist
Sending
[ ] Custom Domains
[ ] Sending the video in the 2nd email
[ ] Spintax
[ ] Low volume per inbox (35/day) - Use smartlead.ai or maility.io or instantly.ai to rotate inboxes to send a high volume of outreach
For each inbox, you want to send a max of 35 emails per day (700 a month) including followups.
You can purchase inboxes from Pitchlane at £40 an inbox, this covers a .com domain for a year, cost to Zoho for a year, and linking to your sending software instantly/smartlead.
[ ] Keep bounce rate per campaign lower than 2% by using email cleaner - https://neverbounce.com/
[ ] Only send to business emails
Fundamentals
[ ] Warm your email domain for 14 days
[ ] DKIM, DMARC, SPF - check with https://mxtoolbox.com/
[ ] Check if your domain has been blacklisted - http://mxtoolbox.com/blacklists.aspx
[ ] Minimum 5 minute time gap between sending emails