We are having trouble sending to Yahoo and Aol accounts among others. In Aol and Yahoo if we send the exact same email using two different sending addresses 1 gets delivered and 1 gets blocked. We are sending from email@example.com and from firstname.lastname@example.org the later gets through and former doesn't. Both are coming from the same mail server. Our IP as a PTR and is not blacklisted anywhere that I can find. Also the spam score using barracuda is a .2 and using spam assassin is a 1.2. All messages that get delivered are placed in the spam box but the headers show that they were never flagged as spam. When I look up the IP reputation on AOL is shows neutral.
I guess what I am asking is why Yahoo would block mail from 1 domain and not another considering they both come from the same mail server? and if we are not blacklisted how do we find out if Yahoo or AOL has internally flagged us due to complaints?