Customers email flagged as spam by their supplier email spam filter ( after a www hack now resolved

My new clients 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 []
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
    host [*.**.**.**]
    SMTP error from remote mail server after end of data:
    550 A URL in this email (zzzzz. ie) is listed on Please resolve and retry
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ITguy565Connect With a Mentor Commented:
I would probably run their domain though this
Once I determined what was going on, then I would look at possibly getting them removed from the blacklists or informing them how to remove themselves from the blacklists.
Brian BConnect With a Mentor EE Topic Advisor, Independant Technology ProfessionalCommented:
There are instruction on the website on how to get delisted temporarily as part of fixing the problem. Most of these RBLs don't really care about what your problem is, so you have to follow their rules to be delisted.

Optionally whoever was rejecting your email can whitelist you, but you would have to ask them directly.
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