Best Cold Email Platforms: Avoid Bounced Emails and Slow Support - Recommendations Needed

Hi folks! Could you share your favorite platform for sending cold emails and warming up? I’m currently using Smartlead, but I’m consistently encountering bounced emails in their warm-up service, which, in my opinion, is not acceptable. The support is slow, and despite my repeated attempts to request a fix, I’m still experiencing bounced emails during the warm-up process. Also, one inbox was disconnected from warm-up yesterday, and even after 24 hours, the support hasn’t provided any response on fixing it. This is quite frustrating – it raises concerns about the foundation of the service. If I’m encountering bounced emails during warm-up, then what service am I actually paying for? This is not a complaint; I’m just reaching out to see if anyone can suggest a similar platform without the problems I’ve explained above. Thank you in advance!