On Thu, 28 Jun 2018 at 13:27, kazabe <kaz...@gmail.com> wrote: > Hi, > > I'm have a very strange issue with a mail server, locate in the main > company office. Until the last five weeks we are experimenting > problems to deliver emails to some domains stored on outlook.com and > other servers. We message stay on our queue with the status 442 like > this: > > "dsn=4.4.2, status=deferred (lost connection with > mail.server.com[XX.XX.X.XX] while receiving the initial server > greeting)." > > We discard from our side any issue related with rbl, wrong ehlo > config, spf, dkim and firewall but the issue continue. > > I connect my own laptop directly to the ISP router (to discard our > mail server or firewall completly), and do some connection test > ... > >
> This dont happen with all the servers, but i see to is a common issue > when the destination server have other isp. > > So, this is the question: why if both ports are "open", just the 587 > permit to complete the connection? > > Is possible to the ISP have some internal rules to "block" the traffic > related with some connections related with the port 25 of others ISP? > (i do the same test with 10 email servers where i know to use our same > ISP without problems)? > > Im confused because this issue dont happen with all the port 25 > connections; just with some email servers, specially outlook.com, but > microsoft answer us to they dont have problems related with our IP. > Some ISPs may do this, I have seen something like it in Turkey. Could it also be that you are sending from dynamic ip and it is being rejected for this reason? In any case the solution is to relay emails through another server (which doesn't have the same problem) using STARTTLS on port 587.
