[CentOS] sendmail sending out on port 587
Gregory P. Ennis
PoMec at PoMec.Net
Sun Mar 21 22:47:12 UTC 2010
On Sun, 2010-03-21 at 16:18 -0500, Les Mikesell wrote:
> Gregory P. Ennis wrote:
> > Dear List,
> > I recently spent some time out of the USA, and found myself in a hotel
> > that blocked port 25 which prevented my laptop's ability to connect to
> > my office mail server. I did a scan on the internet and made the
> > observation that this was a common problem. I had port 22 available so
> > I was able to get my office server set up to accept mail on 25 and 587
> > without difficulty. The command "telnet mail.server.com 587" to my
> > office mail server connects without difficulty.
> > However, I have not been able to get sendmail on my laptop to connect to
> > sendmail on my mail server at home using port 587.
> > I have added the following to sendmail.mc on my laptop without success :
> > define(`RELAY_MAILER_ARGS', `TCP $h 587')
> > define(`ESMTP_MAILER_ARGS', `TCP $h 587')
> > I finally made it back home, but have decided to change my configuration
> > to use 587 by default so that this problem will be avoided, but I have
> > been unable to get my laptop to connect.
> > Anyone having ideas would be appreciated.
> Usually you would block 587 inbound on your own office firewall and use that to
> distinguish between locally-submitted mail and internet-received. You
> definitely don't want to permit relaying from un-authenticated internet sources.
> If you need access to other office resources, one approach would be to set up
> openvpn on an office server and the laptop so you have an encrypted connection
> through the firewall. Another would be to set up sendmail to require
> authentication on port 587 and also set up your laptop to send authentication.
I appreciate your advice about having un-authenticated relaying, and
understand the importance of having this blocked. My sendmail office
server will only allow relaying with authentication using :
define(`confAUTH_OPTIONS', `A p y')dnl
My problem is using port 587 on the laptop sendmail that is trying to
send e-mail to my office sendmail server. I have been unable to get
sendmail on the laptop to connect to the office server using port 587.
Your idea of using openvpn is interesting. I have not experimented with
this yet, but will download it and take a look. My presumption is that
it needs to be on both the laptop as well as office server.
If you have other ideas would appreciate your assistance.
Thanks for your help!!!
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