Cant receive mail from gmail " 554 5.7.1 : Relay access denied"

[sahsanu]

That error occurs because your server is using an open DNS resolver, such as 1.1.1.1, 9.9.9.9, etc.

To fix it check out this post:

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.