The idea of SMTPing email out from your home ISP turned out to be problematic once spam became a business model. Gmail's not the only place that categorically won't trust it.
You need a mail server. You can run it yourself if you're in to that sort of thing, but you can't run it off a residential/consumer uplink. Sorry, this one's non-negotiable. Then your home server authenticates to your mail server as a client, and send email through your mail server. Your mail server is recorded as the IP address of origin, not your home address. MTAs are already designed to do this with nearly zero effort on your part, so you don't have to change your workflow, just your config file.
Don't want to pay for a mail server? Good news! There's like a gazillion services that actually do this for free. Gmail actually turns out to be one of them. Don't want to have to use Oauth? Good news! Gmail's not the only mail service. There's ten billion others.
You need a mail server. You can run it yourself if you're in to that sort of thing, but you can't run it off a residential/consumer uplink. Sorry, this one's non-negotiable. Then your home server authenticates to your mail server as a client, and send email through your mail server. Your mail server is recorded as the IP address of origin, not your home address. MTAs are already designed to do this with nearly zero effort on your part, so you don't have to change your workflow, just your config file.
Don't want to pay for a mail server? Good news! There's like a gazillion services that actually do this for free. Gmail actually turns out to be one of them. Don't want to have to use Oauth? Good news! Gmail's not the only mail service. There's ten billion others.