The situation with outlook got much worse in our overnight runs. We
transferred 7K subscriber emails to relays ending in outlook.com and
saw the following feedback in our logs:
MaxConnections: 83, Connection: 1386, RateLimited: 6392
where the following regexp is used in our log post-processor:
MaxConnection -- "^.*: to=<.*>.* said: 451 4.7.652 The mail server .*
has exceeded the maximum number of connections.*$"
Connection -- "^.*: lost connection with.* while sending RCPT TO.*$"
(and the like)
RateLimited -- "^.*The mail server .* has been temporarily rate
limited due to IP reputation.*$"
We made three changes to our configuration yesterday:
(1) smtpd_tls_security_level = none & smtp_tls_security_level = none
in main.cf as we do not need TLS and do not have it configured. We
are now seeing "conn_use=" in our logs for the first time.
(2) outlook unix - - n - 6 smtp
-o syslog_name=outlook
-o smtp_connection_cache_on_demand=no
(3) we increased our email arrival rate from 500 to 1000 over the past
two days. this is likely a primary factor.
I looked for domains that *are not* using the outlook: transport but
are using the outlook.com relay servers. There are 383 such domains
-- the vast majority are one email address per domain. These domains
are competing for the limited number of outlook.com connections and
they are not being controlled by the outlook: transport process limit
in master.cf. Adding 383 domains to outlook: in transport.regexp
seems a bit extreme and would be impossible to maintain. How can we
control the number of connections made on behalf of this set of
domains to the outlook.com relay servers?
My solution, without additional input, is to reduce our email arrival
rate from 1000 to 500 emails per minute. I will also reduce the
outlook: processes to 2 in master.cf and
"outlook_destination_concurrency_limit = 2" in main.cf in hopes this
will minimize the feedback log messages we are seeing from outlook
relay servers. This "solution" is Very constraining. The google.com
relay servers can transfer 10,000 emails per minute without a single
feedback message in the logs. This "solution" is limiting the
delivery rate of ALL domains at the expense of the outlook.com
connection limitations. I hope there is a better solution!
Thanks, Greg
www.RayStedman.org
