Spam Bouncebacks

Hello Experts,

We have hosted exchange through Microsoft office 365.  Recently we have had a number of clients that receive bounce back emails stating that they are being blocked because they are seen as spam.  I have created a exception in our exchange account for a couple of the domains that are having trouble getting through to us and they still get a bounce back.  Is there anything that has changed with email since the start of the new year, or does anyone have any incite on what's going on?

Thank you,

-GTS
GalaxyTechServiceAsked:
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Owen RubinConsultantCommented:
Are you hosted on a shared server provider? I have seen this in cases where another user on the shared server is spamming. Sadly, the IP of the shared server is the same or similar for both of you, so if they get blocked, you get blocked.

Even if you are on a non-shared server, if others at the hosting provider are causing a lot of spam from addresses in the same class address space, you might get included.

Contact your hosting provider and have them move you to a new server, or deal with the blacklist that is causing users to be unable to reach you.

It only takes one bad apple on a shared host to cause problems with all hosts on the server, or even the host address space.
Vasil Michev (MVP)Commented:
What is the exact reason, can you post the full NDR? Office 365 uses several blacklists, if their domain have ended up in one of these, they will have to remove them first. There can be a dozen other reasons, so post the full NDR.
GalaxyTechServiceAuthor Commented:
Vasil Michev, this may help.
Document1.pdf
David Johnson, CD, MVPRetiredCommented:
missing dmarc and spf records
GalaxyTechServiceAuthor Commented:
David Johnson, the sender is?
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