Mailing list archive access glitches

Over the past few days I've frequently had attempts to
fetch a https://www.postgresql.org/message-id/... URL
fail with reports like

    Error 503 Backend fetch failed

    Backend fetch failed

    Guru Meditation:

    XID: 89820252

    Varnish cache server

It eventually works if I reload enough times.  Discussion
on Discord says that other people have seen this too.

The problem seems noticeably worse right now ...

            regards, tom lane