🚀 go-pugleaf

> I have been getting the following bounces back.  Does anyone know what
> causes this error?

I don't know, but I'm willing to guess at part of the problem.

> 354 Start mail input.  End with <crlf>.<crlf>
> 554-Mail not delivered to some or all recipients:
> 554 Mailer problem: can't read error log.

The 554 message is supposed to be triggered by a level U error detected
in the mail processing, and the 2nd line of the 554 should then be the
text of one or more type-U messages saved in an error log along the way.
I'm guessing that some bug in the handling of some presumed error
condition is causing Mailer to fall through into the 554 code without
ever generating a type-U error message, so that Mailer can't find any
excuse for not delivering the mail to all recipients.  Mailer therefore
puts out a fall-back message admitting that something funny is going on.
Beyond that, I'm afraid my guessing skill plays out.  I suppose the
first thing to do is see if the problem recurs and, if so, whether
anything bad happens in sending mail individually to each of the
three recipients in this example.
                                      John