improvMX for domain email forwarding

In a previous post, I had mentioned using our domain registrar's free email service. Now I have moved away from that to improvMX, for a hopefully more stable performance - emails were taking around 20 minutes to be forwarded using our domain registrar's mail severs, and this was causing problems with one-time passwords (OTPs) sent by Github, for example. There is a way to send emails via gmail smtp servers, too (but it displays "via ourdomain.tld" when I use my account@ourdomain.tld ).