[wp-trac] [WordPress Trac] #64420: Default Envelope Return-Path can tarnish IP reputation for mail-sending hosts.

[WordPress Trac]

#64420: Default Envelope Return-Path can tarnish IP reputation for mail-sending
hosts.
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 Reporter:  dmsnell       |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Future Release
Component:  Mail          |    Version:  6.9
 Severity:  normal        |   Keywords:
  Focuses:                |
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 [61010] introduced a change which set the Envelope Return-Path for emails,
 when unset, to a default value which could be a plausible and deliverable
 address, whereas previously it was set by the running host to an
 undeliverable address using private details for the username and hostname.

 While this has improved the deliverability of messages sent from WordPress
 by providing DMARC and SPF alignment, an issue was raised from the host
 perspective.

 Some hosts appear to be applying global policies on their email servers
 which allows deliverability at the otherwise undeliverable mailboxes,
 making it possible to send bounce emails and thus helping to maintain IP
 reputation.

 It appears that much of the confusion appears because of the integration
 of many different systems which have all evolved in complicated ways over
 time, but there might be ways to adjust which move the WordPress ecosystem
 forward while helping hosts avoid misconfiguration issues on individual
 sites from reflecting on their servers.

 This ticket branches from #64368 where a specific interaction bug between
 the `sendmail` configuration and the email changes caused unexpected
 crashing.

 == Goals

  - WordPress should send valid emails with proper Envelope Return-Paths.
  - Misconfiguration relating to non-deliverability should be easier to
 identify and resolve for site owners.

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Ticket URL: <https://core.trac.wordpress.org/ticket/64420>
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