Postfix : Host Not found

Action: failed
Status: 5.4.4
Diagnostic-Code: X-Postfix; Host or domain name not found. Name service error
    for type=A: Host not found

Above is what I get when I send email to New Postfix Server.

(Host Name and Domain Name is correctly set +mxtoolbox complains for reverse DNS ).

I need to fix it ASAP. Please help.
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Look whether locally that name resolves as well.
The problem s that the entry does not seem as coming from postfix.

Do you have local dns for while it is also dns served externally?
Also contact your ISP and have them create a PTR record for your sending IP which matches the A record.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
amit_panjwaniAuthor Commented:
@arnold - when I do nslookup - I get a list of name servers for this mail server. That should be ok.

@ papertrip - I believe thats some thing already done - anything diagnostics that can verify that
Big Business Goals? Which KPIs Will Help You

The most successful MSPs rely on metrics – known as key performance indicators (KPIs) – for making informed decisions that help their businesses thrive, rather than just survive. This eBook provides an overview of the most important KPIs used by top MSPs.

No, that is the problem. The local dns server must resolve the ip rather than refer the application to another source of information.
You can configure your local name server to resolve for local subnets.
Once you correct this, you should not have this issue.
You said initially that mxtoolbox said reverse did not match.  If you want to check from another external source then just put your sending IP into and make sure it resolves to whatever the A record is for your sending server.
amit_panjwaniAuthor Commented:
Allow me to compound this problem :(

I was running sendmail earlier on same server - (Same DNS settings). I was able to receive emails from Gmail and yahoo - No issues.

I was able to send emails (External mail relay)

AFTER - Switching to Postfix :

Now - I can send mails (External relay server). But I cannot receive any emails. Thats the point where I get this error : Host not found.

Please help
The error than is not from postfix but from exchange?
You have to be on the system that generates the email and check its configuration.
Try to cobble together information will lead to unrelated suggestion that could make matters worse.  Run lsof -i:25 where postfix is installed an see what is being reported.
amit_panjwaniAuthor Commented:
@arnold I know what you are trying to suggest . I had already uninstalled sendmail - before I pushed for Postfix.

I think I have resolution. It was all ISP issue -  Static IP resolves bit differently.

I have raised ticket and they are going to resolve it in next 6 hours.

Thank you!
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.