Emails are bouncing suddenly

From last 2 days my email are bouncing me back don't know the reason for this I checked my server and domain is not in blacklist.
Here is the message I got in bounce email.

host []
    SMTP error from remote mail server after end of data:
    550 permanent failure for one or more recipients (

Please help me in this.
John MartynAsked:
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Dr. KlahnPrincipal Software EngineerCommented:
I checked my server and domain is not in blacklist.

There are tens of different major blacklists and probably hundreds of smaller ones.  All it takes to get your mail stopped cold is to be listed on one.  Which lists did you check?

It appears that your domain is using the Barracuda Networks email as outgoing MTAs.  That being the case and Barracuda's servers being reputable as far as spam, it is unlikely that the MTA's IP address or the MTA's domain name is causing the issue.

550 permanent failure for one or more recipients (

500 level errors mean that retrying won't solve the problem.


This section of the message seems to indicate that this site, or this specific user has manually blocked you or your domain as a sender.

a) What is the nature of the email you're sending?
b) Is your domain forwarding through Barracuda's server, or is it sending as itself and Barracuda is just the last outgoing MTA?
c) What is the CIDR block of your originating system?
d) Do you have a valid SPF record for your domain?
e) Is there a valid DKIM record for your domain?
f) If there is a DKIM record, is the MTA sending a signed digital signature?

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To improve on Dr. Khlan answer:
are you getting bounces for _ALL_ your email, some emails or just the emails sent to that recipient ( ( ?
In the former case, you should look at issues with your configuration (SPF, dkim and so on). In the latter, it is possible you've been blacklisted by that particular recipient.
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