If that's what they're selling, they're not very good at it. Sendgrid doesn't support all applicable RFCs, and they don't support spool, so, they have exactly 0% deliverability if the recipient host is down for any reason, or uses greylisting.
I've never had any issues with mail from my WiFi IP accepted. You'd normally send it just to your own server from your local laptop w/o any extra configuration, so, it's up to you how you configure your own server. I just tried sending to Gmail directly from Postfix on my MacBook, without any extra configuration, and it's been accepted by Gmail as well. Zero configuration on the laptop. Postfix and the mail CLI clients come preinstalled, and the mail just works.
I've never had any issues with mail from my WiFi IP accepted. You'd normally send it just to your own server from your local laptop w/o any extra configuration, so, it's up to you how you configure your own server. I just tried sending to Gmail directly from Postfix on my MacBook, without any extra configuration, and it's been accepted by Gmail as well. Zero configuration on the laptop. Postfix and the mail CLI clients come preinstalled, and the mail just works.