I have 3 mail servers (One Microsoft Exchange and two Mailmax). The mailmax servers have 100+ domains on each. I also have a Spam filtering server (Vircom) that is used for 80% of the domains we host.
I want to configure Sendmail as a backup mail server that will receive and store mail whenever one of our server is down and will resend mail to the mail server when it come back up. I don't wan't to list each mailbox on Sendmail (this woul'd be a nightmare to manage), only the domains.
DNS entries look like this :
sendmail.hosting.com. IN A 22.214.171.124 (This would be the new Sendmail server)
exchange.domain1.com. IN A 126.96.36.199
domain1.com. IN MX 10 exchange.domain1.com.
domain1.com. IN MX 20 sendmail.hosting.com.
mailmax.domain2.com. IN A 188.8.131.52
domain2.com. IN MX 10 mailmax.domain2.com.
domain2.com. IN MX 20 sendmail.hosting.com.
vircom.domain3.com. IN A 184.108.40.206
domain3.com. IN MX 10 vircom.domain3.com.
domain3.com. IN MX 20 sendmail.hosting.com.
The Sendmail version installed is 8.14.3.
I found on this site many way to do it but I am not sure wich one is the best for our needs.