Matthew Kitchin via Postfix-users:
> On 5/22/2025 3:33 PM, Wietse Venema via Postfix-users wrote:
> > To be precise, Postfix delivers the message with the 'good' display
> > name in the From: header. The unexpected change happens after Postfix
> > has delivered the message to some other system.
> >
> >> Maybe Azure SMTP is doing something to the message. I am not sure.
> > The chain is:
> >
> > Thunderbird > Postfix -> Microsoft cloud > your mail user agent
> >
> > The change could happen in Microsoft cloud, or in your
> > mail user agent.
> >
> > Maybe your mail user agent (Thunderbird?) is overriding the display
> > name when it does not match the email address in the address book.
> > That cloud be a security feature.
> I agree. At this point, it seems it is happening in Azure SMTP. Results
> are the same no matter the client.
I'm not so sure that Azure is the culprit.
How many mail *READING* programs have you tried? The display name
replacement can happen in mail reading programs. Thunderbird
has many options to control how the sender is displayed.
> > That's the same one as logged by Postfix, and confirms that
> > this is message matches the Postfix logging.
> Now for the ultimate Irony. Azure SMTP has a daily limitation we could
> exceed. Normal Office 365 Basic Auth email services are going EOL, so
> they push you to "High Volume Email" services which is really still part
> of O365. HVE has the same restrictions as Azure, but also DOES check the
> header from address. If it isn't the specified account address, it
> rejects it with a very clear message. So, I ironically now do have to
> use a header check. I was close, but I couldn't get it to work
> correctly. I wanted to rewrite the header from address but keep the
> display name. I was about to post here, but tried ChatGPT instead. It
> took refining the question a few times, but wow. That is really cool
> that is gave me this.
> /^From: (.*<).*@.*(>)/ REPLACE From:
> ${1}carespot-donotre...@carespot.com${2}
CAUTION: this is not needed. Your canonical mapping already does a
better job: it fixes both the sender address in the header and in the
envelope (the MAIL FROM command).
Your PCRE only replaces the sender in the From: header, but not the
envelope sender (in the MAIL FROM command). Azure will definitely
object to that unauthorized envelope sender.
> Wietse, Victor, and others. It is awesome that you still support this
> project at this level. I was a heavy user from about 2005 to 2012, but
> work took me down another path. It was too funny to immediately see an
> email about a pflogsumm update after 11 years. It took about the same
> break I did. Great stuff and impressive dedication and longevity.
Everything has changed except for the basic SMTP and MIME protocols.
Wietse
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