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Cannot send mail outside of domain

Cobra25 asked
Hey guys,

I can send mail internally and to Gmail, but doesnt seem to be else where. Why is this?

This is Exchange 2007 on SBS 2008.
Watch Question

What does the non-delivery reports say? Are you using yourself as mail server (based on MX) or you're using a smart host?
cpmcomputersManaging Director

Check for available disk space
exchange does this if there is insufficient space
Viral RathodConsultant

1) Make  sure your IP Address is not blacklisted , check the same using following url.


2) Check Queue viewer Under Toolbox and check the reason if e-mail stuck on the same.

3) Try to send e-mail to other domain using Telnet and check the results.
Viral RathodConsultant

@ cpmcomputers : Sir, Internal Mail flow is working fine so there will be no issues with disk space.
Also try this tool,

If you are facing issues where your outgoing Emails are consistently rejected by other servers or land up in Junk Email or SPAM folders of the recipient mail box, this test can help you in identifying the problems.

Testing Process

Send an Email to test@allaboutspam.com
That email will bounce with a URL in the bounce messge.
Either click on the URL or Copy/paste the URL in a browser.
You will see report on your Email Server.
cpmcomputersManaging Director

Exchange server enters back pressure mode when available disk space drops to around 2%.
Viral RathodConsultant

@ cpmcomputers : Sir, ,Yes that's true , If exchange server found there is a back pressure mode that time exchange server will stop transport service and will not allow internal or external mailflow until the  disk space has drops to normal .
Please don't mind.
cpmcomputersManaging Director

It has three modes
Normal medium and high
In medium internal works but not external
(If this is the problem it will be reported in the event viewer )
Will take seconds to verify or eliminate it S a cause ?
cpmcomputersManaging Director

If it's not disc space
I would looking next at either the receive connector or a DNS resolution issue
@viral is correct in suggesting looking at what is happening in the queues
Mohammed KhawajaManager - Infrastructure:  Information Technology

As the issue is with sending, I assume you can receive email from all other domains (i.e. yahoo.com, outlook.com, etc.).  In this case then you need to look at your send connector(s).  Your send connector may be configured to relay messages to gmail.com but no other external domains.  Your send connector should be configured to route email to all domains (i.e. *)
check your ip or domain if is Blacklisted
check your  Connection Filtering or Port 25 blocked at the remote site
check this link :