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Can MTA send mail via a relay without being told so?



The 2019 Stack Overflow Developer Survey Results Are Inrelay mail from one postfix server to anotherZimbra doesn't send mail via smtp relay anmorePostfix: 'Relay access denied' - all incoming mail is rejectedSetting up SPF and initial questionsUsing SPF for spoof protectionCan't send mail from own server to GoogleAllowing a partially trusted server to send mail for one given address via SPF / DKIMSPF with -all includes directive with ~all?Setting SPF record for mail relay servers to avoid softfailSPF setup for mail and relay server



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5















I'm thinking of adding an SPF to a domain. So I'm concerned if there are circumstances under which my MTA would use some relay when sending mail. Like, when the destination servers are too busy or something? I'm mainly interested in postfix's or exim's default settings.










share|improve this question






















  • On the sending site MTAs can use long chains of relays, that’s typical In an enterprise setting, passing through site local installations, enterprise Gateways, spam filters and possibly a public cloud/isp service for sending, The chain is however configured or enforced privately. Once the public MTA sends it only picks a primary or secondary MX. It is not uncommon to use secondary MXs of your provider and your filtering must deal with it. It is however something you configure with your MX DNS records, so it is configured by the recipient admins.

    – eckes
    Mar 30 at 20:34

















5















I'm thinking of adding an SPF to a domain. So I'm concerned if there are circumstances under which my MTA would use some relay when sending mail. Like, when the destination servers are too busy or something? I'm mainly interested in postfix's or exim's default settings.










share|improve this question






















  • On the sending site MTAs can use long chains of relays, that’s typical In an enterprise setting, passing through site local installations, enterprise Gateways, spam filters and possibly a public cloud/isp service for sending, The chain is however configured or enforced privately. Once the public MTA sends it only picks a primary or secondary MX. It is not uncommon to use secondary MXs of your provider and your filtering must deal with it. It is however something you configure with your MX DNS records, so it is configured by the recipient admins.

    – eckes
    Mar 30 at 20:34













5












5








5








I'm thinking of adding an SPF to a domain. So I'm concerned if there are circumstances under which my MTA would use some relay when sending mail. Like, when the destination servers are too busy or something? I'm mainly interested in postfix's or exim's default settings.










share|improve this question














I'm thinking of adding an SPF to a domain. So I'm concerned if there are circumstances under which my MTA would use some relay when sending mail. Like, when the destination servers are too busy or something? I'm mainly interested in postfix's or exim's default settings.







email postfix exim spf






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Mar 30 at 13:45









x-yurix-yuri

443716




443716












  • On the sending site MTAs can use long chains of relays, that’s typical In an enterprise setting, passing through site local installations, enterprise Gateways, spam filters and possibly a public cloud/isp service for sending, The chain is however configured or enforced privately. Once the public MTA sends it only picks a primary or secondary MX. It is not uncommon to use secondary MXs of your provider and your filtering must deal with it. It is however something you configure with your MX DNS records, so it is configured by the recipient admins.

    – eckes
    Mar 30 at 20:34

















  • On the sending site MTAs can use long chains of relays, that’s typical In an enterprise setting, passing through site local installations, enterprise Gateways, spam filters and possibly a public cloud/isp service for sending, The chain is however configured or enforced privately. Once the public MTA sends it only picks a primary or secondary MX. It is not uncommon to use secondary MXs of your provider and your filtering must deal with it. It is however something you configure with your MX DNS records, so it is configured by the recipient admins.

    – eckes
    Mar 30 at 20:34
















On the sending site MTAs can use long chains of relays, that’s typical In an enterprise setting, passing through site local installations, enterprise Gateways, spam filters and possibly a public cloud/isp service for sending, The chain is however configured or enforced privately. Once the public MTA sends it only picks a primary or secondary MX. It is not uncommon to use secondary MXs of your provider and your filtering must deal with it. It is however something you configure with your MX DNS records, so it is configured by the recipient admins.

– eckes
Mar 30 at 20:34





On the sending site MTAs can use long chains of relays, that’s typical In an enterprise setting, passing through site local installations, enterprise Gateways, spam filters and possibly a public cloud/isp service for sending, The chain is however configured or enforced privately. Once the public MTA sends it only picks a primary or secondary MX. It is not uncommon to use secondary MXs of your provider and your filtering must deal with it. It is however something you configure with your MX DNS records, so it is configured by the recipient admins.

– eckes
Mar 30 at 20:34










2 Answers
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11














No, if you don’t configure any relay (and don’t fiddle around on the network layer) , an MTA will try to deliver to whatever DNS says should get the mail.






share|improve this answer






























    4















    I'm concerned if there are circumstances under which my MTA would use
    some relay when sending mail.




    No. Your server will attempt to send email to the server whose host is described by the MX record(s) for the destination domain.






    share|improve this answer

























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      2 Answers
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      2 Answers
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      11














      No, if you don’t configure any relay (and don’t fiddle around on the network layer) , an MTA will try to deliver to whatever DNS says should get the mail.






      share|improve this answer



























        11














        No, if you don’t configure any relay (and don’t fiddle around on the network layer) , an MTA will try to deliver to whatever DNS says should get the mail.






        share|improve this answer

























          11












          11








          11







          No, if you don’t configure any relay (and don’t fiddle around on the network layer) , an MTA will try to deliver to whatever DNS says should get the mail.






          share|improve this answer













          No, if you don’t configure any relay (and don’t fiddle around on the network layer) , an MTA will try to deliver to whatever DNS says should get the mail.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Mar 30 at 13:53









          SvenSven

          87.7k10148200




          87.7k10148200























              4















              I'm concerned if there are circumstances under which my MTA would use
              some relay when sending mail.




              No. Your server will attempt to send email to the server whose host is described by the MX record(s) for the destination domain.






              share|improve this answer





























                4















                I'm concerned if there are circumstances under which my MTA would use
                some relay when sending mail.




                No. Your server will attempt to send email to the server whose host is described by the MX record(s) for the destination domain.






                share|improve this answer



























                  4












                  4








                  4








                  I'm concerned if there are circumstances under which my MTA would use
                  some relay when sending mail.




                  No. Your server will attempt to send email to the server whose host is described by the MX record(s) for the destination domain.






                  share|improve this answer
















                  I'm concerned if there are circumstances under which my MTA would use
                  some relay when sending mail.




                  No. Your server will attempt to send email to the server whose host is described by the MX record(s) for the destination domain.







                  share|improve this answer














                  share|improve this answer



                  share|improve this answer








                  edited Mar 31 at 1:32









                  Lightness Races in Orbit

                  275416




                  275416










                  answered Mar 30 at 16:53









                  joeqwertyjoeqwerty

                  96.6k465149




                  96.6k465149



























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