How to troubleshoot the mail error 550 5.7.1 in Linux reseller hosting?

How to troubleshoot the mail error 550 5.7.1 in linux reseller hosting?

Error: 550 5.7.1: Message rejected as spam by Content Filtering (Exchange Server)

The most common SMTP error code when sending email is 550.

SMTP error 550 is a generic error message. It means the email could not be delivered.

An SMTP error 550 delivery failure happen for a variety of reasons; while the error code 550 itself tells you nothing about the cause of failure, many an SMTP server includes an explanatory message with the error code.Often, an email could not be delivered because it has been blocked as spam, either through an analysis of its contents or because the sender—or sender’s network—is listed as a probable source of spam in a DNS blacklist.

If you’re receiving this error, it means your email message was sent from a server or domain that is currently listed as a high volume spam source by a reputable global black list.This problem may also occur if the owner of your domain name has been using the domain for spamming or fraudulent purposes.

1.Spam email
2Bulk email
3.High complaint rates
4.Lots of invalid recipients

Check the IP address or domain listed in the error message against reputable RBLs including Spamhaus. An excellent RBL checking tool is available at www.mxtoolbox.com.

Find out if your domain has been listed by Spamhaus using the “Domain Lookup Tool” in the URL listed below. If the domain is listed, request delisting the domain.

https://www.spamhaus.org/lookup/

Secure your account against compromise by performing the following:

1.Change your password. Ensure your new password has a minimum length of eight characters and uses a mixture of upper and lower case letters, numbers, and special characters.

2.Verify that your operating system is running with the latest security updates.
Update your anti-virus software and conduct a full scan of your system to ensure that a spammer has not installed spam-sending malware on your computer.