Re: [exim] Intermittent gmail SMTP failures: "Authentication…

Top Page
Delete this message
Reply to this message
Author: Bill Brelsford
Date:  
To: exim-users
Subject: Re: [exim] Intermittent gmail SMTP failures: "Authentication Required"
On Tue Feb 22 2022 at 12:34 PM +0000, Jeremy Harris via Exim-users wrote:
> On 21/02/2022 21:18, Bill Brelsford via Exim-users wrote:
> > I get a significant number of failed SMTP sessions at gmail
> > (smtp.gmail.com::587). Connections start the same, but fail
> > when exim appears to not send an AUTH LOGIN command:
>
> > Suggestions? Thanks.
>
> Get a debug run of a fail. Work out from the sequence why.


Yes, thanks (I should have known to do that..). When it works:

    DNS lookup of smtp.gmail.com (A) succeeded
    fully qualified name = smtp.gmail.com
    smtp.gmail.com 74.125.20.108 mx=-1 sort=-295 
    ...
    gethostbyname2 looked up these IP addresses:
      name=smtp.gmail.com address=74.125.20.108
    74.125.20.108 in hosts_require_auth? yes (matched "smtp.gmail.com")
    scanning authentication mechanisms
      SMTP>> AUTH LOGIN
      ...
      SMTP>> MAIL FROM:<gnxl@???> SIZE=1244 AUTH=abc@xyz


When fails:

    DNS lookup of smtp.gmail.com (A) succeeded
    fully qualified name = smtp.gmail.com
    smtp.gmail.com 74.125.195.108 mx=-1 sort=-96 
    ...
    gethostbyname2 looked up these IP addresses:
      name=smtp.gmail.com address=74.125.195.109
    74.125.195.108 in hosts_require_auth? no (end of list)
    74.125.195.108 in hosts_try_auth? no (option unset)
      SMTP>> MAIL FROM:<gnxl@???> SIZE=1244


It gets a different IP address (.109 vs .108) when looking up hosts
in hosts_require_auth, so fails. Why does it do a second DNS lookup
for the target host?

As a workaround I added "hosts_try_auth = *", which works. I first
tried "hosts_try_auth = 74.125.0.0/16", but it still showed "option
unset" and failed (why?).

Bill