What 4xx/5xx rejection codes could mean at the various stages of an #SMTP transaction:
▻https://wordtothewise.com/2014/05/smtp-level-rejections
Infovore, father, photography, roller-skating, cycling, Africa, Free software, open networks, adventure, wargaming, cooking and more geekery
What 4xx/5xx rejection codes could mean at the various stages of an #SMTP transaction:
▻https://wordtothewise.com/2014/05/smtp-level-rejections