Today I heard that a customer can't send email to us. He received the following error:
< #5.5.0 smtp;550 [ipaddress] is not allowed to send mail from [domain name]. Please see http://www.openspf.net/Why?scope=mfrom;firstname.lastname@example.org;ip=xxx.xx.xxx.xxx> #SMTP#
How is that possible? I searched the Internet for a possible solution, but I'm not sure what it is. When I go to openspf.net it seems like the records from the sender are wrong, but why is it that email to our company is blocked and email to other companies don't get blocked?
Is it possible that our domain is blocking the email with our spam filter? Or has it nothing to do with our own domain and does the sender have wrong records?