I recently created a new VPS and installed an email server using Modoboa.
Everything seemed to be working and fine until I sent an email to an @icloud.com address. The iCloud user never got my email, but I got his. Due to this being so soon after installing my mail server (literally 20 minutes) I put it down to that and didn't think much of it.
Days later I got the following email from my mail daemon:
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<EXAMPLE@icloud.com>: host mx01.mail.icloud.com[17.42.251.10] refused to
talk to me: 550 5.7.0 Blocked - see
https://support.proofpoint.com/dnsbl-lookup.cgi?ip=95.217.218.207
Reporting-MTA: dns; mail.eml.pm
X-Postfix-Queue-ID: C5CD042368
X-Postfix-Sender: rfc822; EXAMPLE@eml.pm
Arrival-Date: Mon, 15 Mar 2021 08:36:29 +0100 (CET)
Final-Recipient: rfc822; EXAMPLE@icloud.com
Original-Recipient: rfc822;EXAMPLE@icloud.com
Action: failed
Status: 4.7.0
Remote-MTA: dns; mx01.mail.icloud.com
Diagnostic-Code: smtp; 550 5.7.0 Blocked - see
https://support.proofpoint.com/dnsbl-lookup.cgi?ip=95.217.218.207
I've sent an email to Proofpoint asking to be unblocked, but I'm not sure if that's how it works.
I've also opened a ticket with my VPS provider asking for a new IP address but they're yet to respond, and I doubt they'll do this for free.
My email is still received just fine by Yahoo! and Gmail (I just tested these two).
I added all mail server ports to be allowed through my firewall so I was sure this wasn't the issue, but just to be super sure I took down my whole firewall for testing and I still get this issue.
My server's IP (https://who.is/dns/mail.eml.pm to get it if you need it - IPV4 and IPV6) is said not to be blacklisted here: https://www.spamhaus.org/query/ip/95.217.218.207.
Does anyone know what's happening and how to fix it? I'm new to email servers, so I'm sorry I couldn't be more helpful in my explanation.