[CentOS] [Off topic] sending mail from Comcast was: Sendmail not working

Sun Apr 19 18:25:34 UTC 2020
S.Bob <sbob at quadratum-braccas.com>

I followed this guide:


now I get this:

# echo "Subject: sendmail test4" | sendmail kevink at psalm19pix.com
[root at kdb-bugs auth]# echo "Subject: sendmail test4" | sendmail -v 
kevink at psalm19pix.com
kevink at psalm19pix.com... Connecting to [] via relay...
kevink at psalm19pix.com... Deferred: Connection reset by []
Closing connection to []


On 4/19/20 11:08 AM, Jason Pyeron wrote:
>> -----Original Message-----
>> From: Tim Evans
>> Sent: Sunday, April 19, 2020 12:50 PM
>> On 4/19/20 12:38 PM, S.Bob wrote:
>>> On 4/19/20 10:36 AM, Tim Evans wrote:
>>>> On 4/19/20 12:28 PM, S.Bob wrote:
>>>>> All;
>>>>> I installed sendmail via yum, but if I test it like this:
>>>>> The original message was received at Sun, 19 Apr 2020 10:02:56 -0600
>>>>> from localhost []
>>>>>      ----- The following addresses had permanent fatal errors -----
>>>>> <sbob at quadratum-braccas.com>
>>>>>       (reason: 554 5.7.1 Service unavailable; Client host
>>>>> [] blocked using xbl.spamhaus.org.rbl.local;
>>>>> https://www.spamhaus
>>>>> .org/query/ip/
>>>> Is your system's IP address?  If so, as this shows, that
>>>> IP is on spamhaus' blacklist of addresses. Thus, your sendmail is
>>>> working fine.  Problem is elsewhere.
>>>> anything I can do to fix it?
>> Assuming this is your IP address, visit https://www.spamhaus.org/lookup/
>> and request that it be removed from the blacklisted IP's.
>> However, looking at the headers from your message, it appears Comcast
>> may be your ISP, and this IP address appears to be a
>> Comcast address, so you may need to contact Comcast tech support for
>> help in getting the blacklist designation removed.
> There are a few situations here.
> 1. You are a business customer with a static IP, and are entitled to send/receive SMTP by your ISP (Comcast)
> 2. You are a business/residential customer who is allowed to send (not likely allowed to receive) SMTP and you have a domain elsewhere to receive replies to your email
> 3. You are a business/residential customer who is NOT allowed to send SMTP except for your ISP (Comcast) provided email.
> Only you would know which on for sure is you, but it is very likely #3.
> The advice provided previously is for case #1 - contact Comcast and inform them that your contracted services are not working because of .... and you will need to beable to work with them on testing and suggesting fixes. They have a dedicated support phone number (which they provided you if you are actually a #1 type customer - e.g. gigabit pro, metro Ethernet, etc.)
> In case you are a #2 or #3 type customer, you may want to use a smart host configuration - e.g. define('SMART_HOST','[smtp.comcast.net]') . For postfix, use relayhost = [smtp.comcast.net] .
> Now when you send mail to that relay it will relay it. This is provided you are entitled to have your email relayed - contact Xfinity customer service for help there.
> If using this relay does not work, please post the exchange starting with the HELO (check your maillog or do it by hand with telnet).
> --
> Jason Pyeron  | Architect
> PD Inc        |
> 10 w 24th St  |
> Baltimore, MD |
> .com: jpyeron at pdinc.us
> tel : 202-741-9397
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