I use two OpenBSD machines (notebooks) that have configured mutt clients. One of them has OpenBSD 7.0 on it with mutt version 2.1.3, while the other runs OpenBSD 7.1 with mutt 2.2.3 . Both of them use exactly the same mutt configuration file.
Reading emails makes no trouble on neither of the machines. A problem rises when I try to send an email on "newer" (in terms of OBSD version) machine.
I can't send any email from that machine. Trying to send an email to myself results in
SMTP session failed: 553 5.7.1 You are sending spam (check https://lookup.abusix.com/search?q=X.Y.Z.W where
X.Y.Z.W is my ip address.
I am using wired connection to access the network. On older machine (with 7.0 on it) there is no such problem. I can send emails to myself and others.
What can cause such a difference?