Internally we originally used a DNS round robin alias for Connections to connect to to route SMTP emails but that was problematic when one of the servers in the alias was taken off line.
IBM has made this easier by allowing you to use MX records to list the SMTP servers to connect to as detailed in Sending mail from any available mail server.
It was fairly simple using the example in the knowledge center to set this up. Firstly I had our network team create (internal only) MX records for three Domino servers for internal.acme.com with the required weightings. Then I checked out notifications-config.xml and edited the following lines and checked it back in.
<channelConfigs>
<emailChannelConfig>
<useJavaMailProvider>false</useJavaMailProvider>
<smtpJNDILookup>
<smtpJNDILookupURL>dns:///internal.acme.com</smtpJNDILookupURL>
<javamail>
<property name=”mail.debug”>false</property>
<property name=”mail.smtp.connectiontimeout”>120000</property>
<property name=”mail.smtp.timeout”>120000</property>
<property name=”mail.smtp.port”>25</property>
<property name=”mail.smtp.socketFactory.port”>25</property>
<property name=”mail.smtp.socketFactory.fallback”>false</property>
<property name=”mail.smtp.sendpartial”>true</property>
</javamail>
</smtpJNDILookup>
<maxRecipients>50</maxRecipients>
</emailChannelConfig>
</channelConfigs>
At first I left the below line in and it didn’t work.
<property name=”mail.smtp.socketFactory.class”>javax.net.ssl.SSLSocketFactory</property>
Setting <property name=”mail.debug”>true</property> wrote the following to the SystemOut.log.
[2/21/17 20:13:34:309 GMT] 0000023e SystemOut O DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun Microsystems, Inc]
[2/21/17 20:13:34:322 GMT] 0000023e SystemOut O DEBUG SMTP: useEhlo true, useAuth false
[2/21/17 20:13:34:322 GMT] 0000023e SystemOut O DEBUG SMTP: trying to connect to host “domino.internal.acme.com.”, port 25, isSSL false
[2/21/17 20:13:34:347 GMT] 0000023e SystemOut O DEBUG SMTP: exception reading response: javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
[2/21/17 20:13:34:348 GMT] 0000023e SystemOut O DEBUG SMTP: useEhlo true, useAuth false
[2/21/17 20:13:34:348 GMT] 0000023e SystemOut O DEBUG SMTP: starting protocol to host “domino.internal.acme.com.”, port 25
[2/21/17 20:13:34:349 GMT] 0000023e SystemOut O DEBUG SMTP: exception reading response: javax.net.ssl.SSLException: Connection has been shutdown: javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
Remming out the aforementioned line referencing allowed me to connect over port 25.
To test this my colleague stopped the SMTP listener on the Domino server with the lowest weighting causing it to connect to the next server.
collaborationben 