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I have some problems with my postfix setup. We send newsletter regulaly to our customers once or twice a week. and we have expierenced that many customers do not get their emails, it's simply because our domain has been listed as spammer in their spamfilter.

I've asked one of our customers to check what's the reason that our emails come directly in their spamfilter. he said "the problem is, that we are sending emails from a server which is not registered to be a valid exchanger for domain name [ourdoman].com".

can anyone explain to me what does this mean?

the company use MS exchange as our main mail server. and we use linux / postfix / php to send newsletters. both ms exhcange and postfix share the same domain name.

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  • It is probable that the domain uses DKIM/SKEY and that your postfix server is not included in those records. You should talk to the DNS admins to check what records are in place and have your server added.
    – Jenny D
    Nov 22, 2013 at 14:34
  • If my hostname in postfix is called new-webserver, which make my full qualify domain name to be new-webserver.mydomain.com. can I then send emails to customers as [email protected], or should I send emails out as [email protected]?? – Zhenyu 9 secs ago edit
    – Zhenyu
    Nov 25, 2013 at 9:41
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    Not necessarily. You need to read up on SPF and DKIM, and also read the question linked in on the top here (serverfault.com/questions/48428/…). This issue is a lot bigger than can be answered in a comment here.
    – Jenny D
    Nov 25, 2013 at 14:29
  • This is also a good thread: superuser.com/questions/677780/…
    – toraritte
    Nov 22, 2020 at 10:00

3 Answers 3

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Maybe you have not set a valid ptr-record for your mailserver. the myhostname entry in main.cf should be the same as your ptr record for your mailserver ip. Also check if you have a SPF-record for your domain. If so check if you have listed your postfix mailserver in it.

this statement

"the problem is, that we are sending emails from a server which is not registered to be a valid exchanger for domain name [ourdoman].com"

is quite wrong. A mailserver does not have to be the MX in order to be able to send email for that domain.

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  • Also if you're using a dial up connection with a dynamic ip-address you should consider configuring your Exchange server and postfix to use a "real" mailserver for sending out emails instead of delivering them themselves. As in case of a dynamic ip-address you will not be able to meet the requirements mentioned above.
    – lsmooth
    Nov 22, 2013 at 18:05
  • thanks for you answere. but if my hostname in postfix is called new-webserver, which make my full qualify domain name to be new-webserver.mydomain.com, can I then send emails to customers as [email protected], or should I send emails out as [email protected]??
    – Zhenyu
    Nov 25, 2013 at 9:40
  • you can use [email protected], the myhostname has nothing todo with the sender address
    – ah83
    Nov 25, 2013 at 16:18
  • Hej, another question. my webserver has different ips for incoming and outgoing. which IP should I use in PTR record. the incoming one or the outgoing one? thanks...
    – Zhenyu
    Dec 5, 2013 at 9:11
  • Use the outgoing.
    – ah83
    Dec 5, 2013 at 12:15
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You need to form correctly the headers and try good words in the content of your messages.

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  • Perhaps you could also include examples of what you mention in your answer in order to provide clarification.
    – squillman
    Nov 22, 2013 at 17:12
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If that's truly the issue then you need to make a change to the MX record at the DNS server(s). More info here.

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