I run my development system on Win 10 using xampp. I run my production system on a Namecheap server for a hosting package I have from which I host a number of websites including my production SI site. I currently use the smtp server through my namecheap site for both development and production. In the past, I have also used smtp through my Comcast and Gmail accounts. I haven’t tried those servers since switching to Swiftmailer but I will give them a try on my development system.