2017/5/18 -It started working. It looks like the problem was old DNS cache at mailhub.siol.net. Anyway, thank you very much for helping me.
2014/12/23 -You need a PTR record that resolves 128.199.39.109 to the hostname of your sending server. Might also want to look into SPF records for your domain too.
2017/11/26 -Error 450 4.7.1 indicates that the Exchange server is performing the reverse lookups to identify the address from where you are sending the email.
2019/2/8 -You should be able to force a PTR record through unbound by adding the following to data/conf/unbound/unbound.conf in the server block.
2013/11/22 -Check the DNS settings on the outbound mailserver. Make sure you alse have a PTR record set up for the hostname that is send with the EHLO/HELO ...
2013/11/8 -When a user here sends an email to a particular domain it bounces back with: 450 4.7.1 Client host rejected: cannot find your hostname.
2017/3/3 -Hello, I recently installed mail cow on my VPS box and I getting this error message all the time after when I try to send an email to an ...
2012/9/7 -This error message is seen when you have sent an email and the remote server rejects the email. In your exchange 2010 or Exchange 2007 queue ...