Reverse dns is not a valid hostname как исправить
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Reverse dns is not a valid hostname как исправить

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Ошибка SMTP теста: Reverse DNS is not a valid Hostname. Как можно исправить?

Создал А запись для 3 уровня:
Создал PTR запись для:,
Создал MX запись: > 10
Из-за чего может быть эта ошибка? Не знаю что еще можно сделать.
В /etc/postfix/

#myhostname: #mydomain: #myorigin:



  • Вопрос задан более двух лет назад
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SMTP Valid Hostname > Reverse DNS is not a valid Hostname

I use PLESK 11 on one of my servers, and use NS.mydomain & NS1.mydomain, everything works fine, DNS Zones are OK, reverse DNS is OK.

Except on MXTOOLBOX this :

SMTP Valid Hostname > Reverse DNS is not a valid Hostname
SMTP Reverse > DNS Mismatch OK — 195.154.XXX.XXX resolves to
SMTP Banner Check > OK — Reverse DNS matches SMTP Banner

Tried so many searches on Google, but no response and always 3 same pages from MXTOOLBOX.

Maybe someone can help me (I migrated IP of this server in datacenter, because they ask us to do it), so in /etc/hosts for example I found old IP, I changed it, restart network interface, but always the same thing. postfix too (changed IP and restart).

Thanks for any kind of help.

Basic Pleskian

Maybe it can help, some missing data ?

Basic Pleskian

Last thing to add from MXTOOLBOX :

smtp > mail > Reverse DNS is not a valid Hostname

It seems that the problem comes not with domain, but mail .domain. reverse, any idea on how to fix please ?

Basic Pleskian

I think maybe found why, but don’t know how to fix.

  • domain. and mail.domain. both uses the same IP, so when you try reverse that IP it goes to domain. and don’t go to mail.domain
Basic Pleskian

nobody ? In fact how to set the reverse dns of the IP of server to main .domain name of server & mail.domain
Thanks for any help

New Pleskian
Basic Pleskian

+1 too no response from post date problem not solved.

If you found a solution, please post it here, it can help a lot of people I think.
I found other posts (on other forums) with same problem, no response too.

Plesk addicted!

Plesk Certified Professional

Why you didn’t contact Odin Support Team if this problem so critical for you and community can’t help here?

Basic Pleskian

I think this is support forum of Plesk ? it’s not critical everything works fine, but mxtoolbox tells than it’s not right.


I think this is support forum of Plesk ?

Please click to «» — you will then see in the navigation: «Support» and by moving the mouse over the Support — Navigation, it says clear and without possible interpretation under » Self Service Support «, with 3 possible links to «Knowledgebase», «Documentation» and «Odin Forum». The «Odin Forum» is a community — discussion — forum.

If you would like to get official technical Support ( non-free ! ) from the Odin — Support — Team, please visit:

Basic Pleskian

Hi, thanks for message, before I used parallels forum.

Plesk addicted!

Plesk Certified Professional
Hi, thanks for message, before I used parallels forum.

Sometimes community can’t help because of complexity of problem require investigation directly on server. Therefore we recommend contact support team in such cases.

New Pleskian

Could you complete or confirm this plesk configuration please?

Server configuration:
1. Rename your Plesk server (
2. Configure rDns for your plesk server (configure it with your host provider: 123.XXX.XXX.XXX > and check nslookup)

Domain configuration:
1. Enable mail service on your domain (Postfix or Qmail)
2. Check if MX server is resolved to 123.XXX.XXX.XXX
3. Configure SPF and allow +a +ip4:123.XXX.XXX.XXX
4. Configure mail settings to use DKIM protection

Sent items throw mail client is redirected to spam (hotmail/outlook for example)
To analyze the problem: says 10/10 everything is ok says SMTP Valid Hostname > Reverse DNS is not a valid Hostname

What’s missing? Why plesk documentation or kb not explain the right configuration for skip our mails going to spam? And if no solution, why allow mail service if all mails going to spam or why we have’nt kb to explain this behavior?

Hope someone (Plesk expert) to help us without opening a ticket
Thank you in advance for your feedback


to investigate your issue as described, please include the header section from each eMail, because we can only guess what’s happening at hotmail/outlook . and there is a huge amount of possible issues, so guessing is very time-consuming. A «good» mail — provider shows in the header section, why an eMail is marked as spam.

Another suggestion is to include your configuration files for your mail — server. Once again, we have to guess your settings, which is again very time-consuming and suggestions and/or investigations might not meet your very own settings on your server.

A good advice is to set the hostname of a server to something like:


In addition, your SPF ( and an additional, separate TXT — entry ) would look like:

v=spf1 +a +mx +a:servername.domain.tld +ip4:123.XXX.XXX.XXX ?all says 10/10 everything is ok

If your IP/Domain reputation is good and you are still experience issues with MSN/hotmail, consider setting up «Sender ID verification» ( more information at: )

You could as well sign up for the «Junk Mail Reporting Partner (JMRP) program» and for the «Smart Network Data Services (SNDS)», if you would like to and if you have a lot of MSN/Hotmail mail — reveivers. Please search further informations and how to sign up there, over your desired search engine.

New Pleskian

Thank you very much for your advices, hope it helps someone too.
You have right. The problem is only with hotmail/outlook. Mail is considering as spam automatically when new domain even if IP is neutral
I will investigate and give you a feedback in few days or months.

It seems that Reverse DNS is not a valid Hostname is not a problem

Basic Pleskian

Same problem here, fixed changing rDNS from to

The error says «Reverse DNS is not a valid Hostname» . Is not the same error that «Reverse DNS does not contain the hostname»

New Pleskian

maybe it is the Reverse DNS you use.
You have to fill in the FQDN (fully qualified domain name)
Many Administrators forget that www is part of the FQDN.
So if you have a Reverse DNS «.» try «www.. » as Reverse DNS.

Faris Raouf
Silver Pleskian

Plesk Guru

I came across this issue and wanted to provide a very simple explanation:

If you see «Your Reverse DNS Record (PTR) is not a valid host name» in your MXToolbox results, do not worry. Your email will be delivered. If it is not being delivered, the issue is something else.

In plain English, the error simply means «The IP address of your mailserver has a Reverse DNS record that looks like domain.tld rather than subdomain.domain.tld»

That’s all. Nothing more sinister or worrying. It boils down to «hostname» apparently implying as opposed to just company.tld, which is more of a «domain».

So, if you have an MX record of mail.someplace.tld,
And mail.someplace.tld has an A record of,
Then MX Tooldbox does an rDNS (ReverseDNS) check on

If the rDNS result looks like domain.tld then MX Toolbox will complain with the error in question.
But if the rDNS looks like something.domain.tld instead, then it will not complain
Note that and similar CC domains somehow count as a tld here — so you will still get the error if you have something dot co dot uk rather than subdomain.something dot co dot uk.

As to the WHY this is the case, well, I’m only guessing, but you have to remember that we are supposed to be dealing with mailservers here. Typically, in a non-Plesk, non-simple environment, a mailserver will be a separate box to the web server or whatever. It is therefore likely to have a full hostname like mail.mycompany.tld or similar, rather than a simple domain name like mycompany.tld. And that’s what MXToolkit is looking for. When it sees mycompany.tld instead, the error is generated.

I don’t see the point of this myself, but in the help test for the error, the implication is that strictly speaking, your mailserver should have a hostname that looks like a full hostname and not just look like a domain name.

I could be totally wrong here, but that’s what my tests and research seem to indicate.

Incidentally, if you are rally bothered about the error and want to get rid of it, then just arrange for the rDNS record for the IP address that your MX records eventually point to to have a subdomain and therefore look like a «hostname». e.g. plesk.mycompany.tld or even mail.mycompany.tld rather than look like just a domain (company.tld). This usually needs to be done by whoever has control of your IP addresses — typically the co-lo company, the hosting company, the VPS provider, etc.

Personally, I like to have the hostname of the server match the rDNS of the IP.

New Pleskian

Hi all,
I am afraid that you are not quite right here Faris.
Plesk doesn’t allow to set-up a SMTP banner per domain on a specific server — which is insane as this is EXACTLY why we are licensing such a tool!
The issue is very straightforward. The SMTP banner is that of the main service on the server — say «». When we add,, etc. subscriptions to the server , one would expect to be able to add a new SMTP Banner for each subscription / domain added so that it matches that o f the PTR / mail server sending. Well — it doesn’t as all email will be sent with the SMTP Banner, when the smtp sending is, which PTR is set to exactly what it should for it to work —
And one cannot even set the PTR to cos then it is the PTR that will return a message error — also flagged by the large email services.
Whilst sending all emails for all Subs / Domains on the server from is a recipe for disaster as any client being infected by malware and sending spam thus getting flagged by spam cops would instantly flag the whole server / infect ALL the clients!
This is not for fancy rules setting / trying to be a purist or wast time ! It is specifically / only to keep happy the likes of, and other who have decreed internally that PTR and SMTP banner NOT MATCHING is a spam signal!
Simply do a search on this topic on google. 10s of PLESK clients complaining about the issue, most of them actually knowing what they talk about!
PLESK’s reply? A void silence! NOT EVEN ONE REPLY by PLESK support team!
The result? More and more of my client’s emails are bounced back by the email services of the companies mentioned above, with ZERO possibility other than getting more and more angry about it! Can’t even talk to the PLESK POWER THAT BE about the issue : unless you are a reseller — you are not deemed good enough (even though if am not mistaken am paying good money to them each month for my licenses) for them to deign condescend in talking to you.
I have seem many companies in the past (not a spring chicken anymore) having the same attitude of arrogance. Their name liters the cemetery of failed business — Kodak / Nokia / Psion / Blackberry. ALL OF THEM knew better than their market’s, and refused to talk to clients about their issues / needs.
Till the day when — like what I’ll do next time I change servers and look for a server management company that DOES listen to their client’s issues — said clients started voting with their feet, walking out en masse.
A shame that — as it is indeed otherwise a good product.

New Pleskian

Hi all,
I am afraid that you are not quite right here Faris.
Plesk doesn’t allow to set-up a SMTP banner per domain on a specific server — which is insane as this is EXACTLY why we are licensing such a tool!

A shame that — as it is indeed otherwise a good product.

I believe MailEnable is the weak link for us. They do not seem to support more than one SMTP banner per installation. You can have multiple domains and postoffices, but only one Banner from what I have read and by our testing/examination of their application. For us, it does not seem like Plesk can solve our issue since MailEnable actually performs the SMTP stuff. If you are using a different mail program, you might have more options to use that application to bypass Plesk.

Reverse dns is not a valid hostname как исправить


jimimaseye Moderator
Posts: 9944 Joined: 2011-09-08 17:48

Re: HELO problem /Reverse DNS is not a Valid Hostname

Post by jimimaseye » 2021-06-17 23:26

This is nothing to do with hmailserver host name, it’s your dns records.

Your PTR record is which is a Domain name. The RFC guidelines say that is must be a hostname such as Most systems won’t care that it is a domain, but since it’s against the RFC guidelines, it shows a warning.

5.7 on test.
SpamassassinForWindows 3.4.0 spamd service
AV: Clamwin + Clamd service + sanesecurity defs :

New user

obastard New user
Posts: 5 Joined: 2021-06-17 14:34

Re: HELO problem /Reverse DNS is not a Valid Hostname

Post by obastard » 2021-06-17 23:34

mxtoolbox Говорит «Reverse DNS is not a valid Hostname» но PTR есть

Он пишет в разделе smtp «Reverse DNS is not a valid Hostname», если:

# host has address mail is handled by 20 mail is handled by 10 
# host domain name pointer 

Может exim4 не правильно представляется?

Transcript: 220 ESMTP Exim 4.84_2 Thu, 19 Oct 2017 11:00:59 +0300 [600 ms] Transcript: EHLO Transcript: Hello [] 

Смущает строка: Hello 

Может после «» должно быть пусто? Хотя странно, exim так всегда представлялся.
19.10.17 11:44:08 MSK

Это не Exim представляется


пишет, типа привет чувак, я

constin ★★★★
( 19.10.17 13:10:29 MSK )

А ответ на твой вопрос такой: просто не нравится,что ты используешь домен второго уровня для почтовика. Было бы у тебя типа — он бы не ругался. Но это его половые трудности,забей.

constin ★★★★
( 19.10.17 13:16:40 MSK )

Угу, делай что-то вроде:,,,

kostik87 ★★★★★
( 19.10.17 13:22:05 MSK )


пишет, типа привет чувак, я

Я ж не об этой строке говорил, а о следующей. Эта понятна.

constin просто не нравится,что ты используешь домен второго уровня для почтовика

Ага, понял, спасибо, значит зря «паниковал». ))

Да, изначально так и было. Но на firstVDS не нашли, где «multi PTR прописать», т.е. в PTR добавить еще и — вот и выкрутились доменом второго уровня. Эта 1-я PTR автоматом прописана.

Раньше было, как сказано на форуме. Сейчас такой и кнопки не нашли. ((

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