On Mon, 8 Jun 2020 at 09:54, Forums <forums@mehl-family.fr> wrote:

Hello all.

Sorry for my english I'm french.

I have a private mail server (at home) with my domain name.

I have about 5% of my emails rejected by some SMTP servers for the
following reasons:

- rDNS is KO (my french provider don't give us possibility to create or
modify our rDNS)

Or

- mail server IP comes from a dynamic pool IP (but my IP is static)

So, my idea is to use automatically (managed by Postfix) an alternative
SMTP server (Gmail SMTP with my Google account) when an email is
rejected. But I don't know if it's possible and how to configure that.

I don't think you can send through Gmail smtp using your own domain name on the From header unless you have GSuite, but you can do it with a free low-volume account at Sendgrid.

I am not sure about relaying in the event of rejection, someone else can maybe advise. Alternatively, and assuming your volumes are low, you could just relay all your outgoing mails through [Sendgrid or another].