Postfix experts,
I am using Postfix 2.3.3 on a Centos 5.7 system.
I have a peculiar problem where a client is trying so send out to 1700
local email addresses to our cloud (gmail), but it only seems to be able to
send out a small portion of the list successfully. This person is using
Outlook 10 with the addresses in an Excel spreadsheet to send out an email
form to 1700 users in our Google domain. The first 100 or so users seem to
go out fine, but the rest simply don’t get delivered. So we tried to send
out in smaller bulks such as 100 at a time. That seems to be successful.
Then we tried to send out 200 at a time, the majority went through
successfully, but some randomly did not make it out. Normally when I
examine the maillog I see 4 lines for every successful message, but in some
cases, I only see one line such as:
Oct 31 09:51:55 bclist postfix/smtpd[21089]: 6202C1400BA:
client=unknown[x.x.x.x]
Normally a line like this is followed up with From and To entries. But I
see a number of these just sitting in the log isolated. I suspect these
are related to the ones that are not getting delivered. We have seen
addresses begin dropping after the first 66 entries which feels random.
It feels like if we keep our volume small enough (around 100), we can
succeed. But if we don’t, it seems like some buffer fills up and we start
losing entries. I do sometimes find the following in the logs as well:
postfix/smtpd[21089]: too many errors after RSET from unknown {But I
don’t always see it associated with entries we are losing so I am not sure
if it is really related}.
I should note that we have other offices that use other smtp clients send
out i tens of thousands in bulk weekly without any noticeable problem. So
other clients (albeit not Outlook) seem to work fine.
1. I can’t tell if this might be a Postfix problem or client side
problem.
2. I am pretty much using the Postfix defaults for limits which have
never caused me any problems in the past. So could some limit be causing
me problems?
3. Can some setting relate to buffering?
4. Is there a different setting I might consider on the client
(Outlook) side? Isn’t Outlook only supposed to send out to one recipient
at a time and wait for the results before sending to the next? If not,
shouldn’t Postfix tell it to stop sending if it is getting too much too
quickly?
5. Could The recipient smtp serve(smtp.gmail.com) be causing this
problem by any chance?
Any thoughts are much appreciated.
Tim Tyler
Network Engineer
Beloit College
