On Thu, 8 May 2025, Michael Orlitzky wrote:
On 2025-05-08 08:11:18, Marc wrote:
I used a greylist where emails get a 4xx message with a link that
allows the email through so 'regular' users can get past it. Problem
is, these fucked up networks are not even notifying users about 5xx
and 4xx notifications.
With sendgrid, it depends on the 4xx message, but they often just
silently delete the message. It turns out that, even though the RFCs
explicitly forbid you from doing it, this multi-billion dollar company
has a list of hand-written regexes that they use to "parse" each
rejection message. If the regex decides that a retry is unlikely to
succeed, they delete it.
Most interestingly, they apparently delete messages that get a
connection refused. In the past this was easy to test: turn off your
mail server, do something on Github, turn it back on. The
notifications would never arrive.
They're a spam company whose massive marketing department has tricked
people into thinking they're good for sending transactional email. But
caveat emptor, they treat your password resets and order receipts like
spam too.
If I thought that many users had them enabled,
I would suggest requesting Mail Delivery Reports.
Perhaps I should consider enabling them.
--
Andrew C. Aitchison Kendal, UK
and...@aitchison.me.uk
