Are there any special consideratiuons that I need to be aware of when using Spam Filter ISP Enterprise version when forwarding emails to an Office 365 client - I just cannot get it to work.

In the logfile, it always says "The remote host (xxxxxxxxx.mail.protection.outlook.com:25) disconnected us, - message queued - help@yyyyyyyyyyyyyyyy.com to: zzzzzzzzzzzzzzzz@xxxxxxxxxxxx"

I'm tearing out what little hair I have left   !!!!   BTW, I'm using SpamFilter for ISP v 4.7.2.184 Enterprise

Thanks for your help

Hi Belvoir,

The destination mail server where you're forwarding the emails to needs to be configured to whitelist your SpamFilter's IP address, or many emails will indeed be blocked. Here's an example.

Supposed your SpamFilter receives an email from joe@gmail.com to mike@tradaweb.com.uk, and the destination SMTP server for your domain tradaweb.com.uk is xxxxxxxxx.mail.protection.outlook.com.

Google has an SPF record in the gmail.com DNS that specifies which IPs/hosts are authorized to send emails from @gmail.com. Your SpamFilter's IP is certainly not in that list of authorized IPs... So when xxxxxxxxx.mail.protection.outlook.com receives an email from joe@gmail.com forwarded to it from your SpmFilter, it will reject it because your SpamFilter's IP is not authorized by google to send emails from @gmail.com.

This is just one scenario - there could be other reasons like rate limiters that outlook.com applies for example.

You will need to grant exceptions to allow mail to the Office 365 connectors, as you will be violating SPF & DMARC rules of sending domains when you accept, process & forward mail direct to Office 365.

SPF & DMARC are designed specifically to prevent what you are doing - acting as a man in the middle.