I have looked at a number of maillogs where we receive the 'exceeded
the maximum number of connections' error from the outlook servers.
The following is very telling. The first nine are reformatted
'status=sent' records followed by a 'status=deferred' from outlook. I
obscured the email address and the ip address in the deferred message.
104 - Aug 21 01:35:37, r238, hotmail.com, relay=
104.47.41.33, delay= 0.70, delays= 0.01 / 0.00 / 0.04 / 0.65
105 - Aug 21 01:35:37, r235, outlook.es, relay=
104.47.12.33, delay= 2.30, delays= 0.01 / 0.00 / 0.59 / 1.70
106 - Aug 21 01:35:38, r236, hotmail.com, relay=
104.47.41.33, delay= 0.38, delays= 0.01 / 0.00 / 0.04 / 0.33
107 - Aug 21 01:35:38, r237, hotmail.com, relay=
104.47.41.33, delay= 0.43, delays= 0.01 / 0.00 / 0.06 / 0.36
108 - Aug 21 01:35:38, r238, hotmail.com, relay=
104.47.41.33, delay= 0.43, delays= 0.01 / 0.00 / 0.04 / 0.38
109 - Aug 21 01:35:39, r236, hotmail.com, relay=
104.47.41.33, delay= 0.38, delays= 0.01 / 0.00 / 0.04 / 0.33
110 - Aug 21 01:35:39, r238, hotmail.com, relay=
104.47.41.33, delay= 0.52, delays= 0.01 / 0.00 / 0.04 / 0.47
111 - Aug 21 01:35:39, r238, hotmail.com, relay=
104.47.41.33, delay= 0.67, delays= 0.01 / 0.00 / 0.04 / 0.62
112 - Aug 21 01:35:39, r238, outlook.es, relay=
104.47.12.33, delay= 1.15, delays= 0.01 / 0.00 / 0.31 / 0.83
Aug 21 01:35:40 mail0.raystedman.org r238/smtp[174988]: 12D16CA9684:
to=<foo-...@hotmail.com>,
relay=hotmail-com.olc.protection.outlook.com[104.47.41.33]:25,
delay=0.07, delays=0.01/0.01/0.04/0.02, dsn=4.7.652, status=deferred
(host hotmail-com.olc.protection.outlook.com[104.47.41.33] said: 451
4.7.652 The mail server [xxx.xxx.xxx.238] has exceeded the maximum
number of connections. (S3115)
[DM3NAM03FT010.eop-NAM03.prod.protection.outlook.com] (in reply to
MAIL FROM command))
In this case we have only sent 112 emails when we received the
deferred record. You can also see that the r238 transport was
selected from our randmap a number of times -- which is a valid random
sequence. This entire run sent 7.2K emails to outlook and received
only 8 Max Connection status=deferred records. I conclude that outlook
is actually complaining about the number of connections that are in
use at any point in time.
sender_dependent_default_transport_maps = randmap:{r235,r236,r237,r238}
selects transports at random for delivering email. Is it possible to
schedule a set of transports using a round-robin discipline? This
transport scheduling strategy may avoid the random sequence above
which caused outlook to complain.
Thanks, Greg
www.RayStedman.org
