Firstly -- 14 years! Thank you for your loyalty, we really appreciate it You're absolutely right, and bring up some great points. Unfortunately, that's the nature of shared hosting as well as of email. Anyone can create a blacklist, list an IP, and then either refuse to de-list, or require you to jump through as many hoops as they want. Recipient providers should ensure they are using only reputable lists that are easy for legitimate mail providers to work with to get removed (we use Spamhaus for this reason). If you are not sending bulk email there is nothing you can do to prevent blacklists from happening. You could, however, minimize impact by using a VPS or dedicated machine which would give you your own IP for PHP/webserver mail. Unfortunately, that would not help for client-based SMTP mail.
We'd also like to add that especially when needing to send in bulk or with extra sensitive/critical content/addresses, our regular email hosting may not be the safest option. In general, our web hosting and cloud services are our main focus, and if our email services fail yours and your clients' expectations too often, it may be worth looking into specialized mail hosting services for your domains. Google's mail hosting, though no longer completely free, remains a good option and our panel can help set the DNS for you. There are many others of course, but comparing them would depend on your needs.