Answer

PROBLEM

Email notifications with a large number of recipients are getting blocked. On the dashboard it will appear that Header Checking is blocking those email notifications. 

ENVIRONMENT 

• GFI MailEssentials
• All supported environments

SOLUTION

In the Header Checking log you will see something similar to this:
 
This means that Header Checking found that the email had 19 recipients, so it was tagged as spam.

Maximum number of recipients allowed in email identifies emails with large amounts of recipients and flags them as SPAM. To change this, you have to increase the number in the setting Maximum numbers allowed in MIME FROM in Header Checking.

To increase the number of the Maximum numbers allowed in MIME FROM follow the procedure below:

1. Open MailEssentials configuration
2. Expand Anti-Spam > Anti-Spam Filters
3. Open Header Checking >  General > Maximum number of recipient allowed in email [20]
4. Increase the number of recipients allowed as needed

CAUSE

Header Checking will identify emails with large number of recipients and flags them as spam. The number is compared with the one set in the Header Checking configuration.