Sendgrid is usually spam or redundant notifications, depending on host they might not make it through without manual whitelisting. Additionally, using a totally unrelated SMTP rela to deliver mail defeats much of the point of a self-hosted mailserver, you'd be better off using your local network's SMTP relay.
You control the way you authenticate users, how to run spam filtering, etc.
I run my own on Linode with postfix/dovecot/rspamd linked to LDAP for auth that gets routed through SES (probably some cents per month) and it's working good.
These days it's not easy to circumvent being flagged as spam running your own node, because you can look like any spammer until you prove yourself you're not one which takes time and usually not the best idea and you'd rather use an external relay who will provide you with a better reputation from day one.
If you stick with your own delivery route and friends tell you, your mail isn't arriving as they get flagged as spam, that's your fault.