Recently we've observed a significant increase in website generated spam so we've put together this explanation to break down what is occurring and how to prevent it.
Bots are programmed to search for web forms in order to submit spam content, most websites contain a form, whether it be a contact, subscription, or comment form etc, typically when content is submitted via the form, an email will be generated and sent to notify the website administrator and/or the website visitor.
When a Bot submits spam content through a web form, the spam email/s will be processed by our outgoing mail gateway and subsequently identified as spam and quarantined , the hosting accounts ability to send outgoing mail will be also be suspended.
If your outgoing mail service has been suspended by our mail gateway, you will receive the following bounce back anytime an email is attempted to be sent from that address:
SMTP error from remote mail server after end of data: 451 Your account has been locked. Please contact your administrator
When an accounts outgoing mail service has been suspended, we firstly contact the account holder and acknowledge what has happened with advice on how to resolve, we will then unlock the account so the mail service can continue functioning as expected.
If the account is locked a second time, we will notify the account holder and the outgoing mail service will be suspended until the issue has been resolved on their end.
How can I prevent this?
To prevent bots submitting content you can add a CAPTCHA to your form, a CAPTCHA adds an additional security measure to a web form which helps verify whether the visitor is a bot or a human.
There are various popular CAPTCHA plugins developed for each content management system. As a introductory software, I would recommend taking a look at Googles reCAPTCHA which is compatible with most content management systems
Keep in mind, CAPTCHA will prevent Bots from submitting spam however unfortunately its not possible to stop spam entirely as humans will still able to access and send spam/promotional material.