On Sat, Nov 1, 2025 at 1:50 AM <[email protected]> wrote: > > I've seen several folks lately questioning reduced list activity. > While I'm not sure of the reasonm I've failed to post several times in the > last few weeks. > Mutt has given this response when I try to post: > SMTP session failed: 550 Request failed; Mailbox unavailable > My mail goes out via smtp.mail.yahoo.com and other emails go out with no > trouble. > This message is using Yahoo's web mail as suggested by mrmazda on > forums.debian.net. > We'll se whether this gets through.
I've noticed my GMail spam folder is lighter than usual, too. It has been happening over the last month or two, since September or so (maybe earlier?). My guess is -- and it is just a guess -- major mail providers have become more strict in what they accept, and it is resulting in fewer messages in both my inbox and spam. "More strict" means they are rejecting more messages, and that could be due to DKIM, SPF and ARC header problems. The "550 Request failed; Mailbox unavailable" is a red herring. The SMTP folks did a horrible job at error codes. 550 could mean the user's mailbox is unavailable. But it could also mean a command failed. Or it could mean a local policy violation, like a DKIM or SPF failure. The SMTP folks should have provided specific codes for a specific reason, like DKIM or SPF failure. For completeness, here is the 550 error code from RFC 5321, Simple Mail Transfer Protocol, <https://datatracker.ietf.org/doc/html/rfc5321#section-4.2.2>: 550 Requested action not taken: mailbox unavailable (e.g., mailbox not found, no access, or command rejected for policy reasons) Completely off-topic, I believe the problem is due to the old grey beards who write the standards. They run their own mail servers, and they can diagnose their own problems for their mailboxes. But they failed to foresee that large email providers would emerge, like GMail and Yahoo, and users would not be able to get support. In this case, users are left with generic error messages like 550, which could indicate any number of errors, and no one to help with troubleshooting messages, server configurations or server log files with detailed information. But again, most of this is just speculation on my part. Jeff
