IP Server blacklist check:
If you use SMTP to spam domain mail, 126.com, yahoo, Yandex & aol, Office365, Outlook. You should use it.
Because of private server was not registered with major anti-spam organizations. Unlimited SMTP cannot send inbox to popular email providers like: Gmail, AOL, Outlook, Yahoo...etc
Title & Messenger: Best Good For You.
+ Office365, Outlook, Hotmail ( Junk )
+ Yahoo, Aol ( Spam )
+ Yandex ( Inbox or Spam )
+ 126.com ( Inbox or Spam )
+ Domain mail don't have a system to filter mail, fight spam, Block ads, Block phishing mails: Inbox
Company Emails ( Domain mail ) created from the company server. They don't have a system to filter mail >> Deliver Inbox.
+ Domain mail have a system to filter mail, fight spam, Block ads, Block phishing mails: Inbox or Spam or Not Deliver ( ex: hosting provider: GoDaddy,Hostgator ... etc)
There are many companies buying server or hosting from providers. They also have a system to filter mail. Their email filtering system is weak or strong. DKIM, SPF
Unlimited SMTP easy to pass. if SMTP don't pass. It's mean their email filtering system is strong. >> Not Deliver