we have a website with a SMTP server (Postfix) we used for almost a year. From about yesterday we keep getting the following error when sending emails to hotmail destinations:
Feb 12 10:52:34 CentOS-60-64-minimal postfix/smtpd: NOQUEUE: reject: RCPT from sportilia.com[18.104.22.168]: 554 5.7.1 <firstname.lastname@example.org>: Relay access denied; from=<email@example.com> to=<firstname.lastname@example.org> proto=ESMTP helo=<www.sportilia.com>
I'd like to highlight that we successfully sent email to hotmail addresses since yesterday, but now, without we changed anything on our postfix server, we keep getting this error. I also want to say that we successfully send emails to other domains (e.g. gmail.com).
Any idea on what could be causing this issue? There could be some configuration we could tune to fix it or at least investigate about it?