Mimecast - Email Security Gateway IP Address Updates

Mimecast has recently announced changes to the Mimecast Data Center IP addresses that connect to your and your client's environment. 

You must ensure that these IP addresses are allowed through your firewall, routers, and receives connectors on: 

• SMTP Port 25 
• LDAP Port 389
• LDAP Port 636

Failure to do so will cause delivery issues or LDAP connection issues. For further details, see the following Mimecast KBs: 

• Mimecast IP Address Updates (Updated March 31, 2023)    
• Email Security Cloud Gateway - Data Centers & URLs (Full Comprehensive List based on Region)    
• Email Security Cloud Gateway - IP Address - Frequently Asked Questions      
  • Why is Mimecast making this change?      
  • What happens if I don't make the changes?      
  • How do I test my connection?      
  • If I have IP addresses not on the list provided do I delete them now?