Hello everybody, I am using a Postfix mail relay to modify sender addresses of emails coming from my company Office 365 cloud-hosted domain: I configured a connector on Office 365 to route all emails to Postfix. Everything works perfectly, except for some recipient domains that are also hosted on outlook.com domains. Every mail sent is bounced with this error:
host xxx-xxx.mail.protection.outlook.com[X.X.X.X] said: 554 5.4.14 Hop count exceeded - possible mail loop ATTR1 [xxx-xxx.prod.protection.outlook.com] (in reply to end of DATA command) This error does not appear for every email we send to other *.outlook.com recipients, only for emails sent to domains that have the same *.outlook.com server that we have: searching in Postfix logs, i found that our emails are going out from 3 outlook.com servers, with 3 different IP addresses; I found the same and only 3 IP addresses in error logs related to the bounce error. Here is an example: mycompany-com.outlook.com [104.1.2.3] -> Postfix relay [54.1.2.3] -> recipient_first-com.outlook.com [104.1.2.3] = Bounce error mycompany-com.outlook.com [104.1.2.3] -> Postfix relay [54.1.2.3] -> recipient_second-com.outlook.com [104.4.5.6] = mail sent correctly I suppose that outlook.com considers email coming from the same IP addres as a loop, and then blocks them. Is there a way in Postfix to "mask" (?) source IP and avoid this loop? Do you have better ideas?
