I'm having an issue with Microsoft Exchange and spam being sent from that server. I'm seeing tons of messages from email@example.com going out to unsuspecting users across the web. Some of them have mx-b.mail.citi.com in the header.
Now I wasn't the one who setup this so I'm not sure how to find logs or whatever else you all might need to help isolate the issue. I've changed all of the passwords on my Domain and it's users and have tried to isolate one of the IP addresses I saw within the messages. That part has not worked.
Right now I'm being blocked from sending legitimate emails to gmail and yahoo.