As waplog.com, we have 10 million users. We send approximately 500,000 e-mails per day. We use to use only one mail server mx1.waplog.com. Recently we set up another mail server on mx2.waplog.com and divided our load between these two servers. Our problem is; Microsoft provided emails puts the emails from this new server to junk folder. 

There are no "blacklist" messages from Microsoft in our logs. We believe our IP addresses are not in your blacklist.

There is a discussion about "an IP's reputation" in your troubleshooting page. Would you please send us detailed information about this topic? How can we increase our IP addresses' reputation? What are the other measures we can take to prevent waplog emails from going to junk folder?