why dont you want to use ynotmail? they handle authorization and delivery for you. its a pretty horrible control panel design, but most stuff in porn is poorly designed.
i built my own postoffice for our network, which pushes emails thru a verified smtp. that's a big scale solution tho.
for a single site solution, i use sendinblue (
https://www.sendinblue.com/). you can get dedicated IPs and verify the sender domain. i pay $25 a month and we can send 40k emails a day. we get nearly 100% delivery with that setup and it only takes a simple curl call to send an email.
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