Exim Email Problem: 450 4.7.1 Client host rejected: cannot find your reverse hostname

m0rpheu5

Well-Known Member
Jun 16, 2005
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0
156
Brazil, Curitiba/PR
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Root Administrator
Hello guys, i´m having problems, to send email for some email providers, in all cases that the message stay on my mail queue for 48-72h i got this message when i try to deliver it now:

450 4.7.1 Client host rejected: cannot find your reverse hostname

What could be? i Have RDNS, SPF, DomainKeys, and i don´t know what could be anymore.

Could anybody help me to fix this issue?

Thanks
 

m0rpheu5

Well-Known Member
Jun 16, 2005
75
0
156
Brazil, Curitiba/PR
cPanel Access Level
Root Administrator
Re: Exim Email Problem: 450 4.7.1 Client host rejected: cannot find your reverse host

my actual domain is icnetwork.com.br, many of the clients that i´m sending is hosted in the Locaweb provider (locaweb.com.br), but sometimes i got the same problem with users that is not hosted on there, but normally is.

Thanks
 

m0rpheu5

Well-Known Member
Jun 16, 2005
75
0
156
Brazil, Curitiba/PR
cPanel Access Level
Root Administrator
Re: Exim Email Problem: 450 4.7.1 Client host rejected: cannot find your reverse host

I didn´t see any issue, what issue did you find? i have others server that appears as yeallow equal my domain, and there is no problem.
 

cPanelTristan

Quality Assurance Analyst
Staff member
Oct 2, 2010
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Re: Exim Email Problem: 450 4.7.1 Client host rejected: cannot find your reverse host

Can you please provide the full error message you are getting that includes what IP and hostname it believes isn't resolving properly?

The icnetwork.com.br domain's IP of 186.251.87.30 does return a PTR of br01.icnetwork.com.br which is the port 25 telnet response for the IP as well, so I don't see where there isn't an rDNS functioning.
 

m0rpheu5

Well-Known Member
Jun 16, 2005
75
0
156
Brazil, Curitiba/PR
cPanel Access Level
Root Administrator
Re: Exim Email Problem: 450 4.7.1 Client host rejected: cannot find your reverse host

Ok, follow below two emails that i´m getting error to send emails.

delivering 1Qjs98-0000zQ-0H
Connecting to mx.a.locaweb.com.br [186.202.4.42]:25 ... connected
SMTP<< 450 4.7.1 Client host rejected: cannot find your reverse hostname, [186.251.87.30]
SMTP>> QUIT
LOG: MAIN
SMTP error from remote mail server after initial connection: host mx.a.locaweb.com.br [186.202.4.42]: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [186.251.87.30]
LOG: MAIN
== [email protected] R=dk_lookuphost T=dk_remote_smtp defer (0): SMTP error from remote mail server after initial connection: host mx.a.locaweb.com.br [186.202.4.42]: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [186.251.87.30]

----------------------------------------------------------------------------------------------------------

delivering 1QjrYt-0007tN-Nr
Connecting to mx.a.locaweb.com.br [186.202.4.42]:25 ... connected
SMTP<< 450 4.7.1 Client host rejected: cannot find your reverse hostname, [186.251.87.30]
SMTP>> QUIT
LOG: MAIN
SMTP error from remote mail server after initial connection: host mx.a.locaweb.com.br [186.202.4.42]: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [186.251.87.30]
LOG: MAIN
== [email protected] R=dk_lookuphost T=dk_remote_smtp defer (0): SMTP error from remote mail server after initial connection: host mx.a.locaweb.com.br [186.202.4.42]: 450 4.7.1 Client host rejected: cannot find your reverse hostname, [186.251.87.30]

Thanks.
 

cPanelTristan

Quality Assurance Analyst
Staff member
Oct 2, 2010
7,607
40
248
somewhere over the rainbow
cPanel Access Level
Root Administrator
Re: Exim Email Problem: 450 4.7.1 Client host rejected: cannot find your reverse host

I think you are going to have to contact whoever runs 186.202.4.42 to ask them to check their resolver. 186.251.87.30 does have an rDNS entry, so their resolver isn't accurate at all in that message:

Code:
$ dig -x 186.251.87.30 +short
br01.icnetwork.com.br.