Most link building campaigns fail because of poor deliverability, not bad...

https://wiki-cable.win/index.php/How_Many_Follow-Ups_Should_You_Send_for_Guest_Post_Outreach%3F_The_Science_of_Sustainable_Link_Building

Most link building campaigns fail because of poor deliverability, not bad content. If you’re sending more than 75 emails per day without a properly warmed-up domain, you’re just feeding the spam folder