Error del servidor: '451 Temporary local problem - please try later'

Operating System & Version
centos 7.9
cPanel & WHM Version
94.0.4

JMGarcía

Member
Oct 11, 2016
18
1
3
Spain
cPanel Access Level
Root Administrator
Desde hace unas semanas, algunos dominios alojados en mi WHM tienen rebotes puntuales con el error:

Error del servidor: '451 Temporary local problem - please try later'

Estos errores son puntuales y solo en algunas direcciones de correo y en algunos dominios.

Los dominios están en etc/localdomain
Por si acaso he ejecutado: /scripts/mailperm
La ip del VPS no está listada en ninguna lista negra, las ip de los remitentes tampoco están listadas
Los DNS están bien configurados
El VPS tiene un registro rDSN correcto
El registro MX está configurado correcto
He corregido los permisos desde el WHM y están todos a 751


Y a pesar de todo sigue habiendo errores puntuales,...
Copio un par de errores del log de 2 dominios diferentes:


2021-03-29 20:16:12 H=206-177-77-185.dynamic.conecta-3.es (PCNoel) [XXX.XX.XXX.XXX]:55199 X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no F=<[email protected]> A=dovecot_login:[email protected] temporarily rejected RCPT <[email protected]>: host lookup did not complete

error of another domain:

F=<[email protected]> A=dovecot_login:[email protected] temporarily rejected RCPT <[email protected]>: host lookup did not complete




For a few weeks, some domains hosted in my WHM have bounced with the error:

Server error: '451 Temporary local problem - please try later'

These errors are occasional and only in some email addresses and in some domains.


The domains are in etc / localdomain
Just in case I have run: / scripts / mailperm
The IP of the VPS is not listed in any blacklist, the IPs of the senders are not listed either
DNS is well configured
The VPS has a correct rDSN record
MX record is set correct
I have corrected the permissions from the WHM and they are all at 751

And despite everything there are still specific errors, ...

I copy a couple of errors from the log of 2 different domains:

2021-03-29 20:16:12 H=206-177-77-185.dynamic.conecta-3.es (PCNoel) [XXX.XX.XXX.XXX]:55199 X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no F=<[email protected]> A=dovecot_login:[email protected] temporarily rejected RCPT <[email protected]>: host lookup did not complete

error of another domain:

F=<[email protected]> A=dovecot_login:[email protected] temporarily rejected RCPT <[email protected]>: host lookup did not complete
 
Last edited by a moderator:

cPRex

Jurassic Moderator
Staff member
Oct 19, 2014
6,092
780
313
cPanel Access Level
Root Administrator
¡Hola! Para el dominio que recibe la "búsqueda de host no completada", existen dos problemas posibles. Uno, es que hay una mala configuración en su extremo que causa problemas. Puede verificarlo usando una herramienta como intoDNS: checks DNS and mail servers health para ver si hay errores de DNS, o intentando conectarse al servidor de correo manualmente con este comando desde su servidor local:

Code:
telnet dominioreceptor.com 25
Si alguna de esas dos pruebas muestra problemas, su servidor no podrá enviar correo a esa ubicación remota.

La segunda posibilidad es que tenga un resolutor local incorrecto que no pueda buscar el nombre de dominio. Puede probar esto probando este comando desde su servidor local:

Code:
dig receptordominio.com
y vea si obtiene un resultado. Si no es así, y tampoco hay problemas al verificar el dominio del receptor con la herramienta IntoDNS, puede intentar usar los resolutores públicos de Google en su archivo /etc/resolv.conf para ver si eso soluciona las cosas.

****************************************************************************
Hey there! For the domain that is receiving the "host lookup did not complete" there are two possible issues. One, is that there is a misconfiguration on their end causing problems. You can check that by using a tool like intoDNS: checks DNS and mail servers health to see if there are DNS errors, or by trying to connect to the mailserver manually with this command from your local server:

Code:
telnet dominioreceptor.com 25
If either of those two tests show issues, your server would not be able to send mail to that remote location.

The second possibility is that you have a bad local resolver which isn't able to look up the domain name. You can test this by trying this command from your local server:

Code:
dig receptordominio.com
and see if you get a result. If not, and there are also no issues when checking the receiver domain with the IntoDNS tool, you may want to try using the Google public resolvers in your /etc/resolv.conf file to see if that takes care of things.
 
Nov 27, 2020
15
2
3
Brazil
cPanel Access Level
Root Administrator
2021-03-29 20:16:12 H=206-177-77-185.dynamic.conecta-3.es (PCNoel) [XXX.XX.XXX.XXX]:55199 X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no F=<[email protected]> A=dovecot_login:[email protected] temporarily rejected RCPT <[email protected]>: host lookup did not complete
Hello, I'm facing the same problem for about 2 weeks and I don't know how to resolve it. Because like JMGarcia all the configurations are right, and it only occurs in email software like Thunderbird or Outlook if I use Roundcube or use the email like an alias on Gmail it works well
When I send an email it doesn't go and give error 451, but if I try again it works without any error.
Can you guys help me?
 
Nov 27, 2020
15
2
3
Brazil
cPanel Access Level
Root Administrator
Can you try the test commands I provided to see if your server is able to properly look up that domain name?
Hi, so I made the tests and that is the result
Code:
; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.4 <<>> mydomain.com.br
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1215
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;mydomain.com.br.            IN      A

;; ANSWER SECTION:
mydomain.com.br.     14400   IN      A       xxx.xxx.xxx.xx

;; Query time: 754 msec
;; SERVER: xx.xxx.xxx.xx#53(xx.xxx.xxx.xx)
;; WHEN: Wed Apr 14 09:35:51 -03 2021
;; MSG SIZE  rcvd: 63
and for telnet
Code:
[email protected] > telnet mydomain.com.br 587
Trying xxx.xxx.xxx.xx...
Connected to mydomain.com.br.
Escape character is '^]'.
220-vps.centerlabsp.com.br ESMTP Exim 4.94 #2 Wed, 14 Apr 2021 09:38:20 -0300
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
I was searching about it, and I think in dig all the information is right, but I'm not sure about the telnet.
 
Nov 27, 2020
15
2
3
Brazil
cPanel Access Level
Root Administrator
Those both seem to be returning normal results. If you send a message right now, does that also work?
No, It works sometimes others I get the error 451. Now I get the 550 and I don't know why.
I think it because of a new version of PowerDNS, when I receive the email of the new update was done I started to see these errors. Do you know if powerdDNS can be the cause of these problems?
 

lernierd

Member
Jun 6, 2019
5
2
3
Veracruz, México
cPanel Access Level
Root Administrator
Hi,
Few weeks ago my users started to report the same problem. I've been reading a lot of threads on this forum and tried/checked almost all of them but the error continues. Some say the error is because of an EXIM upgrade. Checking the Mail Delivery reports I can see that almost 100% of the delayed emails are delivered minutes later.

Does anyone know if the "451 Temporary local problem - please try later" error could be triggered by the option (Default to "On") in:

VHM>>Service Configuration »Exim Configuration Manager»"Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam."

Does anyone know when did this option became available in EXIM ?

I'm also working with Version 94.04 over CentOS 7.9..

Thank you ,
--------------------
Hola,
Hace algunas semanas empece a tener reportes de mis usuarios con el mismo problema. He leído y probado casi todo lo que sugieren en este foro pero el error sigue apareciendo.

Alguien sabe si la opción (Acitavada en ON por Default) en:

VHM>>Service Configuration »Exim Configuration Manager»"Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam."

pudiera estar "disparando" el error "451 Temporary local problem - please try later"?

Alguien sabe cuando se integró esta opción en EXIM?.

Yo también estoy trabajando con la Version 94.04 sobre CentOS 7.9.

Gracias
 

cPRex

Jurassic Moderator
Staff member
Oct 19, 2014
6,092
780
313
cPanel Access Level
Root Administrator
¡Hola!

No estoy seguro de cuándo se incluyó la configuración "Introducir un retraso" en cPanel, pero ha estado en el producto desde al menos la versión 82, por lo que no es un cambio reciente. Esto también afectaría solo a los mensajes que llegan a su servidor.

Si necesita ayuda para localizar el problema, no dude en enviar un ticket a nuestro equipo y estaremos encantados de echarle un vistazo.

***********************************************************

Hey there!

I'm not sure exactly when the "Introduce a delay" setting was included in cPanel, but it has been in the product since at least version 82, so that is not a recent change. This would also only effect messages coming in to your server.

If you need help tracking down the issue, feel free to submit a ticket to our team and we'd be happy to take a look for you!
 

lernierd

Member
Jun 6, 2019
5
2
3
Veracruz, México
cPanel Access Level
Root Administrator
¡Hola!

No estoy seguro de cuándo se incluyó la configuración "Introducir un retraso" en cPanel, pero ha estado en el producto desde al menos la versión 82, por lo que no es un cambio reciente. Esto también afectaría solo a los mensajes que llegan a su servidor.

Si necesita ayuda para localizar el problema, no dude en enviar un ticket a nuestro equipo y estaremos encantados de echarle un vistazo.

***********************************************************

Hey there!

I'm not sure exactly when the "Introduce a delay" setting was included in cPanel, but it has been in the product since at least version 82, so that is not a recent change. This would also only effect messages coming in to your server.

If you need help tracking down the issue, feel free to submit a ticket to our team and we'd be happy to take a look for you!
Hi! cPRex thank you for your answer. Yes, you are right. In the thread:
https://forums.cpanel.net/threads/incoming-emails-are-delayed.658441/
a cPanel staff member suggests to turn that option off, but with no success according to the user in trouble. And what about some threads that affirms the problem is caused by a recent EXIM update?

Thank you for your offer. I will open a ticket.

*************

Hola y gracias por la respuesta. Si, usted esta en lo correcto. Hay un post en:
https://forums.cpanel.net/threads/incoming-emails-are-delayed.658441/
en el que un miembro del Staff de cPanel recomienda poner en off esa opción, pero de acuerdo al usuario en problemas, no tuvo éxito. Y que hay acerca de quienes afirman que el problema se debe a una actualización reciente de EXIM?

Gracias por la ayuda y estaré abriendo un ticket.
 
Nov 27, 2020
15
2
3
Brazil
cPanel Access Level
Root Administrator
Hi,
Few weeks ago my users started to report the same problem. I've been reading a lot of threads on this forum and tried/checked almost all of them but the error continues. Some say the error is because of an EXIM upgrade. Checking the Mail Delivery reports I can see that almost 100% of the delayed emails are delivered minutes later.

Does anyone know if the "451 Temporary local problem - please try later" error could be triggered by the option (Default to "On") in:

VHM>>Service Configuration »Exim Configuration Manager»"Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam."

Does anyone know when did this option became available in EXIM ?

I'm also working with Version 94.04 over CentOS 7.9..

Thank you ,
--------------------
Hola,
Hace algunas semanas empece a tener reportes de mis usuarios con el mismo problema. He leído y probado casi todo lo que sugieren en este foro pero el error sigue apareciendo.

Alguien sabe si la opción (Acitavada en ON por Default) en:

VHM>>Service Configuration »Exim Configuration Manager»"Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam."

pudiera estar "disparando" el error "451 Temporary local problem - please try later"?

Alguien sabe cuando se integró esta opción en EXIM?.

Yo también estoy trabajando con la Version 94.04 sobre CentOS 7.9.

Gracias
Hi, I'm still having this problem and like you, I tried everything and nothing works.. I saw that thing about the update too but I don't know if it is.. Do you resolve the problem?
I disabled the "Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam." today but I'm not sure that this will resolve the problem.
Should I open a ticket @cPRex ?
 
Nov 27, 2020
15
2
3
Brazil
cPanel Access Level
Root Administrator
Hi guys, I'm back just to say that "I resolve" the problem. I made a ticket but not in the cPanel, it was on my provider and they changed the /etc/resolv.conf. Just put the resolvers of google
Code:
nameserver 8.8.8.8
nameserver 8.8.4.4
And seems that I'll have no more problems.
But anyway thanks @cPRex for your help and attention.
 
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lernierd

Member
Jun 6, 2019
5
2
3
Veracruz, México
cPanel Access Level
Root Administrator
Hi, I'm still having this problem and like you, I tried everything and nothing works.. I saw that thing about the update too but I don't know if it is.. Do you resolve the problem?
I disabled the "Introduce a delay into the SMTP transaction for unknown hosts and messages detected as spam." today but I'm not sure that this will resolve the problem.
Should I open a ticket @cPRex ?
Hi Anderson,
Sorry for the time to answer. No it is not solved yet. I opened a ticket to cPanel thru my hosting provider and will post the solution as soon as I get it.
Best regards
 
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