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Much more important than SPF and DKIM is Forward-confirmed reverse DNS. You need SPF and DKIM, but before that you need FCrDNS. Without FCrDNS, your server wi

Much more important than SPF and DKIM is Forward-confirmed reverse DNS. You need SPF and DKIM, but before that you need FCrDNS. Without FCrDNS, your server will look like a dynamic IP address. It's also not enough to monitor your own dedicated IP address. You need to monitor your entire /24 IP address neighborhood at your hosting company. You might be sharing the same /24 IP address space as a hacked Wordpress installation and find that Outlook.com will block you just because of that. After that, you might run into issues with large SpamAssassin setups hosting hundreds of thousands of mailboxes blocking your email because of arbitrary rules such as too little text combined with a large image etc. Plain text email will improve your deliverability for these setups.

pbhjpbhj 8y ago
Yes, Microsoft blocked me sending email from my shared hosting to my Hotmail. The email address was whitelisted, and established email back and forth to that domain, and no spam ... but another server at the same host had previously been blacklisted in one blacklist. SPF nor DKIM helped, I don't own the mail server nor want to pay Microsoft's service provider to verify me. In the end I had to bounce the emails from a third-party address. Which you'd think shouldn't work -- certainly not when whitelisting doesn't -- but solved the problem. So to avoid being flagged as a spammer, do the spammiest thing possible: set up a new, free mailbox and bounce your mail from there. SMH.
walrus01 8y ago
rDNS is of course extremely important. That was important even long before the existence of SPF and DKIM. The neighboring IP space and the general IP space reputation of the ARIN/RIPE/APNIC/AFRINIC (or whatever) block assigned to your ISP is extremely important. Your neighbours can ruin everything for you. The only way to ensure that this doesn't become an issue is to host your smtpd at an ISP that has a highly attentive, clueful NOC and responsive abuse policy that actually deals with network abuse (real abuse, not DMCA notices).

pbhjpbhj 8y ago

Yes, Microsoft blocked me sending email from my shared hosting to my Hotmail. The email address was whitelisted, and established email back and forth to that domain, and no spam ... but another server at the same host had previously been blacklisted in one blacklist. SPF nor DKIM helped, I don't own the mail server nor want to pay Microsoft's service provider to verify me. In the end I had to bounce the emails from a third-party address. Which you'd think shouldn't work -- certainly not when whitelisting doesn't -- but solved the problem. So to avoid being flagged as a spammer, do the spammiest thing possible: set up a new, free mailbox and bounce your mail from there. SMH.

walrus01 8y ago

rDNS is of course extremely important. That was important even long before the existence of SPF and DKIM. The neighboring IP space and the general IP space reputation of the ARIN/RIPE/APNIC/AFRINIC (or whatever) block assigned to your ISP is extremely important. Your neighbours can ruin everything for you. The only way to ensure that this doesn't become an issue is to host your smtpd at an ISP that has a highly attentive, clueful NOC and responsive abuse policy that actually deals with network abuse (real abuse, not DMCA notices).