finding undelivered admin emails
We run a number of different servers in my office. We have set them to use our zimbra server as the smtp server for delivery of admin messages. On our zimbra server we have also added an alias domain. The Zimbra server FQDN is email@example.com, the alias domain is mailserv.domain.local (because we found that cron jobs on the mailserv send from firstname.lastname@example.org). The alias domain points mailserv.domain.local to domain.local. We have also setup aliases for email@example.com->admin.domain.local, firstname.lastname@example.org->email@example.com, firstname.lastname@example.org->email@example.com... etc. In our daily admin email there are typically about 50 messages received by the alias domain. Unfortunately, there are typically only about 6 emails in the firstname.lastname@example.org mailbox. I have to assume this points towards something being setup improperly but I have no idea where to start looking. It would be a great benefit to find the emails that are not being delivered by the server. Unfortunately I don't know if this is possible and if it is where those messages would be stored. I'm sure that I can fix the way servers are sending mail but I'd prefer to see which ones need to be fixed and know for sure what I am fixing before I just go off jacking with settings hoping that tomorrow I receive more of the emails that I'm expecting.
Does anybody have any suggestions on places to start? The logs are long each day and to be honest I have no idea what terms I should grep for.