Domain Greylisting
In This article, I am
going to introduce you with a common issue of mail servers called Domain
greylisting (emails are not getting deliver due to domain is greylisted in
commtouch).
Issue:
Emails were getting rejected due to
domain was considering temporary as a Spam sender
Note:
Greylisting is a measure against spam
where the receiving server would reject a message temporarily with a message
after which time to retry, usually within minutes and not later than some
timeout (usually ~ 4 hours). If the sender
waits accordingly and resends the message within the timeout, it will be
whitelisted, otherwise not.
How
to check the domain greylisting
{Note: There
is no exact tool to check the Greylisting of a domain, we can check the log
files and NDR’s for more details.}
How to check domain
whitelisting and blacklisting of domains.
Go to the following links
and check.
Open this link and type
the domain name under the Server Name or Domain and click on Blacklist check.
Image- 1.1
Note:
For testing purpose here I am going to
test the blacklisting of http://www.songs.pk
When you will type the
songs.pk under the domain name and click on blacklist check, you will get the
following result.
Image- 1.2
Note: Here you can see that this domain is showing
blacklisted, it’s mean we are not able to send and receive emails from this
domain, because it seems Spam sender.
How
to verify that domain is whitelisting
Our email server doesn't
seem to understand greylisting. When sending emails to external addresses whose
servers implement greylisting, our MTA seems to retry several times immediately
(which will be rejected for obvious reasons) and then give up and retry only
after hours.
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