Intermittent Spamhaus RBL Blocks for Outlook & GMX on HestiaCP/Exim

[sahsanu]

@eXe

Could someone explain why using Cloudflare’s DNS causes my server to appear as an “open resolver” and end up on Spamhaus, and how I can fix it?

Exim rejecting emails

Because Spamhaus rejects requests for some public dns resolvers. You can: 1.- Disable the spamhaus dnsbl (not recommended) 2.- Change the dns resolver used by your server to one not blocked by Spamhaus like 76.76.2.0 and 76.76.10.0 (Control D Free DNS) 3.- Use your own DNS recursive resolver like bind9, PowerDNS, unbound, etc. 4.- Create a free Spamhaus data query account and you could use your current dns resolvers.