[CentOS] Re: Sendmail problem

Scott Silva ssilva at sgvwater.com
Wed Apr 12 22:50:18 UTC 2006


Thomas E Dukes spake the following on 4/12/2006 4:42 AM:
>  
> 
>> -----Original Message-----
>> From: centos-bounces at centos.org 
>> [mailto:centos-bounces at centos.org] On Behalf Of Johnny Hughes
>> Sent: Wednesday, April 12, 2006 7:28 AM
>> To: CentOS ML
>> Subject: RE: [CentOS] Sendmail problem
>>
>> On Wed, 2006-04-12 at 07:13 -0400, Thomas E Dukes wrote:
>>>  
>>>> -----Original Message-----
>>>> From: centos-bounces at centos.org
>>>> [mailto:centos-bounces at centos.org] On Behalf Of Alexander Dalloz
>>>> Sent: Wednesday, April 12, 2006 7:06 AM
>>>> To: CentOS mailing list
>>>> Subject: RE: [CentOS] Sendmail problem
>>>>
>>>> Am Mi, den 12.04.2006 schrieb Thomas E Dukes um 2:23:
>>>>
>>>>> Here'sanother bounce email:
>>>>>
>>>>> The original message was received at Tue, 11 Apr 2006
>>>> 19:16:44 -0400
>>>>> from localhost.localdomain [127.0.0.1]
>>>>>
>>>>>    ----- The following addresses had permanent fatal 
>> errors ----- 
>>>>> <xxxxxx at comcast.net>
>>>>>     (reason: 521-EHLO/HELO from sender 71.31.91.127 
>> does not map 
>>>>> to localhost.localdomain in DNS)
>>>>>
>>>>>    ----- Transcript of session follows ----- ... while 
>> talking to
>>>>> gateway-s.comcast.net.:
>>>>>>>> MAIL From:<apache at localhost.localdomain> SIZE=2176
>>>>> <<< 521-EHLO/HELO from sender 71.31.91.127 does not map to 
>>>>> localhost.localdomain in DNS <<< 521-sending machine 
>> name must be 
>>>>> provided as a fully <<< 521-qualified domain via 
>> EHLO/HELO command.
>>>>> <<< 521-see section 4.1.1.1 and 4.1.4 of RFC 2821 <<< 521
>>>> 521: Comcast
>>>>> requires that all mail servers must have a PTR record 
>> with a valid 
>>>>> Reverse DNS entry. Currently your mailserver does not fill that 
>>>>> requirement. For more information, refer to:
>>>>> http://www.comcast.net/help/faq/index.jsp?faq=Email118405
>>>>> 554 5.0.0 Service unavailable
>>>> 2 things:
>>>>
>>>> 1) Your mail host at that time of the mail had the hostname 
>>>> localhost.localdomain, thus your Sendmail used it for 
>> EHLO/HELO. You 
>>>> fixed that meanwhile
>>>>
>>>> 2) The remote side requires not only a valid forward DNS record 
>>>> (palmettodomains.com points to that IP) but too a 
>> matching reverse 
>>>> one.
>>>> From here I can't judge whether the named IP is static and thus 
>>>> assigned by your ISP. If that is the case then you really should 
>>>> take care for both types of DNS entries. If not (you are on an 
>>>> dynamic line) you should use your ISP's mail host as SMART_HOST 
>>>> within your Sendmail configuration. DynDNS is a very bad base for 
>>>> reliable mail services.
>>>>
>>>> Alexander
>>> Hello Alexander,
>>>
>>> Yes, I have a dynamic IP address.  If I use my ISPs mail 
>> host as the 
>>> SMART_HOST, would that cause relaying problems?  I tried 
>> that on the 
>>> mail client end a while back and got errors about relaying.
>>>
>>> Thanks, I'll give it a try.
>> Just as a side note here ... the majority of mail servers now 
>> use a technique called Realtime Blackhole List (RBL).
>>
>> Many of the new lists contain the IPs of all dynamic 
>> Cable/DSL providers as a huge amount of spam is sent via 
>> broadband PC's that have been compromised.
>>
>> It is a losing proposition to use dynamic machines to send 
>> reliable e- mail as a server ... at least that has been my experience.
> 
> Hey Johnny,
> 
> Yes, I know.  I have that problem sending mail to AOL (that's ironic) and
> RoadRunner accounts.  If my ISP hadn't lost its mind for what they charge
> ($180/month) for a static/business DSL account, I would be on that.
> 
> Thanks!!
>>  
>>
AOL only wants to send spam, not receive it. You will need to make
arrangements to use a smart host somewhere on a fixed ip with good reverse
mapping. They will need to be contacted to set your domain up as an authorized
relay. You might be able to rent such service monthly, and it should be much
cheaper.

-- 

MailScanner is like deodorant...
You hope everybody uses it, and
you notice quickly if they don't!!!!




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