My new clients email@example.com web site got hacked and spam was sent from it. (www since cleaned up and emails moved to Office365)
I believe their emails may have been hacked before this.
Action taken - moved from a small hosting company to office 365 / exchange
They got a bounce email from a client and it looks like there is reputation damage to the www
From: Mail Delivery System [mailto:Mailer-Daemon@lh23
Sent: 16 April 2018 15:58
Subject: Undeliverable: Date and requirements to date
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
(ultimately generated from firstname.lastname@example.org)
host smtp.antispamcloud.com [*.**.**.**]
SMTP error from remote mail server after end of data:
550 A URL in this email (zzzzz. ie) is listed on https://spamrl.com/
. Please resolve and retry