yes, this is a pain. the blocklist operators either seem to be not so good at vetting abuse reports, or cause collateral damage to get network operators to take

yes, this is a pain. the blocklist operators either seem to be not so good at vetting abuse reports, or cause collateral damage to get network operators to take action (while i don't like getting on a blocklist, perhaps it is having a net positive effect for the wider internet?). i do think mail servers/services are using ip-based blocklists wrong. yes, you can use it as one of many signals. give it some more weight for first-time senders. but if you've been mailing (with spf/dkim/dmarc-authenticated messages/transactions), from an ip that suddenly gets on a blocklist, the previous positive reputation should be stronger than that blocklisting, and you should be able to keep communicating with your known correspondents (until they mark your message as spam after which future deliveries can be rejected/junked). it seems those mail servers/services cheap out and apply ip blocklists early in the smtp process. good for their system load, bad for their analysis performance. in general, it seems even bigfreemail services are bad at using existing reputation in their ham/spam decisions. i recently switched an online webservice i made (that is about sending certain notification by email) to signups via email (like how you can signup to mailing lists: by sending an email to an address). the idea: if you send my service an email, i'm in your list of known correspondents. so the confirmation reply from my mail server (spf/dkim/dmarc-aligned) should certainly be accepted by yours (you much more opt-in do you want?). i tested with some bigfreemails, and yahoo put my reply with confirmation (that even references the original message) in the junk folder. to people who think you can't compete with bigmail: the bar isn't as high as you may think.