IF you configure send mail 1 thread: 50 mails / 1 second = 3000 mails / minute = 180,000 mails / hours
A lot of our customers I like so that. They configure 3 - 10 thread.

CONSEQUENCE:

+ IP Server is blacklist. Out Of Resources.

+ Server Provide report & Suspended - That's why I only sell SMTP for 1 day. It 's very difficult to find a provider that accepts spam mail.
+ You are sending too fast. Server error Why? >>> 2 Simple Reasons for SMTP Server Hangs  ReAd more

How do I send a mass email without being marked as spam?

You should learn ... HOW TO SEND 50,000 - 86,400 mails / day with our Unlimited SMTP: $50  ORDER

Why? Any Server Provide easy report. IP 's very good.

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TYPE 1: Unlimited IP or Domain SMTP ( Normal SMTP ) - What 's delivery rate?

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ABOUT Unlimited SMTP - Full DKIM, SPF, Private Domain, Private IP ( Type 3 )

TYPE 3: Unlimited SMTP PORT: 587 - DKIM, SPF, DMARC - TLS SSL connection - What 's delivery rate?