What's similar between them? A spam host will likely be high volume of similar-looking email sent to users who will never reply and most probably trash/spam-categorize the email. A small, single-user sender will likely be *very* low volume of fairly different-looking email sent to users who will likely answer and otherwise interact with the mail. They have literally nothing in common.
Before I moved to fastmail, my email was consistently getting nullrouted by microsoft. Everything was setup correctly (SPF, DKIM, DMARC, ARC, etc...), and every other mail host I tried would receive my mail correctly. I send out a very low amount of email (3-4 per month?).
Before I moved to fastmail, my email was consistently getting nullrouted by microsoft. Everything was setup correctly (SPF, DKIM, DMARC, ARC, etc...), and every other mail host I tried would receive my mail correctly. I send out a very low amount of email (3-4 per month?).