Hide My Email is the best Apple product you're probably not using. Here's how it can start shielding your inbox and your privacy now, for just 99 cents.
To increase security and reduce the number of unwanted messages, which includes spam, you can restrict Chat message requests from unknown senders in 1:1 conversations and spaces. On your computer,
based around dovecot, but has the basic structure
This might be useful to let some less-certain spam detection to put things into the Spam folder, but hide the more obvious stuff completely.
You can upload your own certificate.
I just put addresses in the file specified by check_recipient_access with REJECT
getting mail lists and DKIM to play together
requires Linux and runs DNS and Postfix in a Docker node
Talkatone http://www.talkatone.com
TextNow http://www.textnow.com - also offers mobile service, similar to Republic Wireless
GrooveIP https://snrblabs.com/GrooVeIp - Android only, limited use for free
Visual voicemail and robocall blocking
YouMail https://www.youmail.com
My Visual Voicemail https://play.google.com/store/apps/details?id=com.vna.service.vvm
CallControl/EveryCall https://www.callcontrol.com/
Truecaller https://www.truecaller.com/
Should I Answer? https://www.shouldianswer.net/
Nomorobo http://nomorobo.com/ free for (some) voip lines
Hiya https://www.hiya.com/products/app recommended by AT&T, freemium