I have a USA based Linux web hosting server. There one IP I’m using shared for all domains. If I sent email from my server to any gmail account the email not receiving gmail account. I have contact with the data center they have replied the below answer:

The message Gmail is providing is:
MTP error from remote mail server after end of data: host alt4.gmail-smtp-in.l.google.com [209.85.143.27]: 421-4.7.0 [IP: xxx.xxx.xxx.xxx 10] Our system has detected an unusual rate of\n421-4.7.0 unsolicited mail originating from your IP address. To protect our\n421-4.7.0 users from spam, mail sent from your IP address has been temporarily\n421-4.7.0 blocked. Please visit http://www.google.com/mail/help/bulk_mail.html\n421 4.7.0 to review our Bulk Email Senders Guidelines.

Can anyone help me to fix this problem?
I have checked blacklist. The server IP is not blacklisted at all.

If you rent server space on a remote server using a web hosting company, can they access your data either stored on the server in files or in a database by resetting the passwords to one that they will know by using an md5 generator? How do I avoid this and is there any way of discreetly watching to see whether the web host is doing this?

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