The bounce back error "550 This message was classified as SPAM and may not be delivered" means that your email was filtered as spam. If its not spam, you may try the following solutions:
Solution 1 - Make sure that SMTP Authentication is enabled in Outlook.
The Microsoft Outlook email client seems to be causing email messages sent through it to score higher than normal, causing emails that otherwise would be allowed through to be classified as spam. This is most commonly caused by not having SMTP Authentication set in the Outlook. You should then be able to send normal emails properly via Outlook.
Solution 2 - Check your email content
Our email servers are using spam evaluation process that is set to the safest levels. This means it is difficult for your emails to be tagged as spam and prevented from going out unless they have a lot of features of a spam like messages or behavior. However if you are still getting caught by the filter, you will want to evaluate both the subject line and body content of the message to ensure there are not any references to popular spamming terms. Attachment also plays a role as known exploitable extensions poses security threat.
Solution 3 - Contact our Support Team
If you have attempted solutions one and two above and are still getting caught by the outbound filter, you will want to contact us and filing a ticket. When emailing please include the entire bounce email, including the headers and our support team will then take the email and find its records in the filtering logs to see why it was blocked.
What is outbound SPAM filtering?
All our shared servers implements a customizable spam filtering tool that evaluates each incoming emails, while outbound SPAM filtering is a process where any outgoing emails will be analyzed to the most common spam like content or behaviour. The outbound is not customizable on an account level and is being handled by our server admins. The filter checks for multiple characteristics and assigns points for any it finds. If the email reaches a certain level or scoring, it will be classified as SPAM and will not be allowed to leave the server. If you are receiving a bounceback with the error "550 This message was classified as SPAM and may not be delivered", then the email you sent has not passed our outbound filter.
Take note that all email can always be determined to be spam based on content. Your incoming spam scoring can always be adjusted in your cPanel >> Spam Assassin scoring.
Why are you doing this on outbound emails?
Outbound screening is a standard process where most reliable web hosting provider implement to help preserve our server's IP reputation. If any email server's IP gets enough spam complaints, it will be reported and blacklisted by most RBL or blacklisting service. Any email server that subscribes to that RBL service, will then block any mails coming in from blacklisted IP address.
It is also possible that any emails coming from any of our servers eventually ends up being delivered to spam folders, regardless of the IP address of the server. As most of our customers do legitimate business online, it would be unfair to allow our server IPs to be classified as spam because of a few abusers, hence the outbound spam evaluation.
