Unable to send emails via client or webmail

[MikeSF]

My boss informed me he was unable to send emails.
Since I wasn't at work, I checked with our provider who told me that the service needed to be updated through WordPress.
I did the needed updates, but the error persisted.
Checking the work accounts, all emails bounce back with this error message:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[email address redacted]
host gmail-smtp-in.l.google.com [74.125.201.26]
SMTP error from remote mail server after end of data:
550-5.7.28 [162.214.71.239 1] Our system has detected an unusual rate of
550-5.7.28 unsolicited mail originating from your IP address. To protect our
550-5.7.28 users from spam, mail sent from your IP address has been blocked.
550-5.7.28 Please visit
550-5.7.28 https://support.google.com/mail/?p=UnsolicitedIPError to review our
550 5.7.28 Bulk Email Senders Guidelines. n8si155462iom.66 - gsmtp

While this email was to a google address this happens regardless of the recipient.

 

[cPanelLauren]

This indicates that your email IP is being reported as having sent spam email. If you're on a shared server you should contact your provider for assistance with this.