Author: John Jetmore Date: To: Haynes, Jonathan CC: exim-users@exim.org Subject: Re: [exim] NULL characters in SMTP command - random errors
On Thu, Mar 15, 2018 at 11:30 AM, Haynes, Jonathan via Exim-users <
exim-users@???> wrote:
> Since upgrading to 4.90-1 every so often we get log messages of the
> following form
>
> 2018-03-14 12:15:05 SMTP syntax error in "RCPT TO:<xxx?xxx@???>"
> H=mail-wm0-f46.google.com [74.125.82.46] I=[138.250.49.234]:25 NULL
> character(s) present (shown as '?')
> 2018-03-14 23:25:04 SMTP syntax error in "RCPT TO:<XXXXXXX@cra?field.ac.uk>"
> H=mail-qk0-f181.google.com [209.85.220.181] I=[138.250.49.234]:25 NULL
> character(s) present (shown as '?')
> 2018-03-09 10:56:00 SMTP syntax error in "R?PT TO:<XXXXXXX@???>"
> H=mail-yb0-f193.google.com [209.85.213.193] I=[138.250.49.234]:25 NULL
> character(s) present (shown as '?')
> 2018-03-07 10:21:52 SMTP syntax error in "BD?T 27127 LAST" H=
> mail-it0-f66.google.com [209.85.214.66] I=[138.250.49.234]:25 NULL
> character(s) present (shown as '?')
>
>
> (I have masked the actual email addresses)
>
> So NULLs suddenly appear anywhere in the SMTP command, sometimes in the
> email address, sometimes the verb etc. In every case the NULL is a
> replacement for a real character not additional. When Exim sees these it
> returns a 501 so if this is part of a RCPT command the sender gets an NDR.
> It appears they are only coming in RCPT and BDAT commands but that may be
> coincidence. There are not a huge number - it seems to be between 2 and 10
> a day. However all seem to be from google servers, although from several
> different ones.
>
