Sendgrid is useful to send email in a homelab setting if you're sending less than 100 emails/day (in my case it's currently 1, when backups complete each day)
First we want to create a sendgrid account, and get our DNS setup following sendgrids guides.
In Proxmox, we need to install a couple things in the terminal:
sudo apt install postfix postfix-pcre mailutils libsasl2-modules
Edit the /etc/postfix/main.cf file and add/update the following lines