vCenter appliance won't use mail relay server

Question

tl;dr: - sendmail is configured to use a relay server but still insists on using 127.0.0.1 as the relay, which results in mail not being sent.

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We have the open source vCenter appliance (v 5.0) managing our ESXi cluster. When connected to it via vSphere Client, you can configure the SMTP relay server to use by going to Administration > vCenter Server Settings > MAIL. There you can set the SMTP Server value. I looked through their documentation and also confirmed on the phone with support that all you have to do to configure mail is to put in the relay IP or fqdn in that box and hit OK.

Well, I had done that and mail still wasn't sending. So I SSH into the server (which is SuSE) and look at /var/log/mail and it looks like it's trying to relay the email through 127.0.0.1 and it's rejecting it. So looking through the config files, I see there's /etc/sendmail.cf and /etc/mail/submit.cf. You can configure items in /etc/sysconfig/sendmail and run SuSEconfig --module sendmail to generate those to .cf files based on what's in /etc/sysconfig/sendmail.

So playing around, I see that when you set the SMTP Server value in the vCenter gui, all that it does is change the "DS" line in /etc/mail/submit.cf to have DS[myrelayserver.com].

Looking on the internet, it would appear that the DS line is really the only thing you need to change in order to use a relay server. I got on the phone with VMWare support and spent 2 hours trying to modify ANY setting that had anything to do with relays and we couldn't get it to NOT use 127.0.0.1 as the relay. Just to note, any time we made any sort of configuration change, we restarted the sendmail service.

Does anyone know whats going on? Have any ideas on how I can fix this?

Answer 1

On Red Hat systems, there's an /etc/mail/access file for sendmail.

And example of the contents is:

# Check the /usr/share/doc/sendmail/README.cf file for a description
# of the format of this file. (search for access_db in that file)
# The /usr/share/doc/sendmail/README.cf is part of the sendmail-doc
# package.
#
# by default we allow relaying from localhost...
Connect:localhost.localdomain           RELAY
Connect:localhost                       RELAY
Connect:127.0.0.1                       RELAY
172.16.2.116                            RELAY
172.16.2.17                             RELAY

You should define your vCenter's IP in that file (or its SuSE equivalent) and restart the daemon.

Edit:

I assumed you set Sendmail to listen on something other than its loopback address. Go into the sendmail.mc file and look for this stanza.

dnl # The following causes sendmail to only listen on the IPv4 loopback address
dnl # 127.0.0.1 and not on any other network devices. Remove the loopback
dnl # address restriction to accept email from the internet or intranet.
dnl #
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl

You want to comment-out the last line there by adding dnl. So you should end up with:

dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl

Restart the sendmail service and try again.

Edit:

The OP is trying to configure their Linux-based vSphere appliance to relay through another mail server. This is just a case of defining a SMARTHOST. In your sendmail.mc file, find the line that says:

dnl define(`SMART_HOST', `smtp.your.provider')dnl

Remove the comment line and enter the name of your mail server. If your mail server's name is mail.bootylicious.com, your resulting sendmail.mc line will look like:

define(`SMART_HOST', `mail.bootylicious.com')dnl

Please make sure that you can ping the name you use...

Restart Sendmail.

Answer 2

There are two configuration files that newer versions of sendmail work with. These are submit.cf and sendmail.cf. Do not change either sumbit.mc (which is used to produce submit.cf) or submit.cf itself. They are used when a local mail program forks sendmail in order to send email and all they do is to relay the mail to be sent to the sendmail daemon that listens on 127.0.0.1:25

So all you need to do is either change DS by hand in sendmail.cf and give it a value like:

DS[relay.server]

including the brackets, or modify the SMART_HOST macro in sendmail.mc:

define(`SMART_HOST', `[relay.server]')dnl

If you modify sendmail.mc you need to produce a new sendmail.cf and then restart the sendmail daemon. In Debian you run sendmailconfig. In CentOS you run both /etc/mail/make followed by service sendmail restart. I am not using SuSE, sorry.

Answer 3

This is bizarre, but this is the only way I could get it to work ...

The name I wanted it to be masqueraded with is mydomain.com. The vCenter server had a hostname of mycluster with mycluster and mycluster.vmware.com in the /etc/hosts file (why vmware.com, I have no idea... is this required for the appliances or did our contractor that configured it do it wrong? Or does the appliance do it by default? Anyone know?).

To get everything working, I had to add mydomain.com to the /etc/hosts file of the vCenter server for both 127.0.0.1 and ::1. But not only that, I had to have it listed BEFORE the mycluster and mycluster.vmware.com. It would appear that sendmail looks at /etc/hosts and grabs the first name listed under 127.0.0.1 and sets that as the sending domain??

Anyway, it works now. When a trigger in vCenter goes off and sends an email, vCenter reports that it could not send the email, but then about 60 seconds later I actually get it. So something still isn't right, but at least it's working.

Answer 4

The following worked for me on Suse Enterprise Linux 11 SP2:

vi /etc/sysconfig/sendmail


# change SMARTHOST to your relay
SENDMAIL_SMARTHOST="[x.x.x.x]"

# change to YES, to not resolve DNS
SENDMAIL_NOCANONIFY="yes"

SuSEconfig --module sendmail

service sendmail restart

Answer 5

My solutions was to add the 127.0.0.2 to the host file.

sudo sh -c 'echo "127.0.0.2 server1" >> /etc/hosts'