1) webmailer not smtp (since webmail yahoo can send up to 500 emails per account immediately, and smtp only 100 per hour). Whatch this software for reference: http://www.blackbulkmail.com/

example:
login to account

1st send >> 100 emails
2st send >> 100 emails
3st send >> 100 emails
4st send >> 100 emails
5st send >> 100 emails

2) now pause (that i can choose in milliseconds) and switch to next account yahoo

3) when there's an error in sending it has to output an "invalidrecipients.txt" file, so i can resend them again

4) backconnect rotating proxy like https://starproxies.com/billing/clientarea.php?action=productdetails&id=3668  add your ip to whitelist
login username: camo090@hotmail.it
pass: Hairefuso1!

here's a few private proxies too:
167.160.72.80:4444:0a2c553903:ocYTzNWF
209.163.117.180:4444:0a2c553903:ocYTzNWF
167.160.74.194:4444:0a2c553903:ocYTzNWF
168.91.11.84:4444:0a2c553903:ocYTzNWF
162.244.150.229:4444:0a2c553903:ocYTzNWF

5) spintax title and description: https://imgur.com/a/dWJwR8O

6) "If" feature to close all the popups when zennoposter will login into the yahoo accounts