Postfix Lost connection analysis: 421 4.4.2 host error: timeout exceeded

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In this post we’ll show the analysis of another common error for smtp status code 421 4.4.2 host Error: timeout exceeded which refers to network or connection problems between SMTP servers. The symptoms you may observe is the your Postfix (IMSVA) server is not able to accept all incoming mails and sender server is starting to have queuing problems. Continue reading

Extended status codes (SMTP)

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The different situations that can be described with the main smtp status codes defined in RFC 2821 are not enough to consider the wide range of situations an MTA server may face when delivering a message. Because of this, a new set of codes were created. The following is an extract from RFC 3463, where a definition for this new SMTP Protocol feature is given: Continue reading

What is Sender-ID?

Sender-ID or Sender-ID Framework (SDIF) is an experimental protocol designed to allow any SMTP Server to validate the fact that the domain used in the incoming mails is legally used and approved by the real owner of such domain. By using records similar to the ones used by SPF, an SMTP Server may obtain detailed information about the authorized servers that are allowed to that domain name. Continue reading