So, I just yesterday updated the Indigo mini to Yosemite, and it appears to have broken email for me as well.
My script still works fine, but emails are not being sent out from the computer. I suspect that I had set up a mail relay through another server, or I had set up some SMTP authentication that didn't survive the upgrade from mountain lion.
So one quick way to narrow down the problem is to type "mailq" on the command line of the server in question. I suspect that you will find a whole bunch of mail messages listed with various error messages. If it returns nothing, then the script is broken, to troubleshoot that, I'd remove the final pipe at the end into sendmail, replace that with a > to a file and verify that the script is producing something that looks like a good email, with proper headers and mime formatting.
If you do have a bunch of messages in your mail queue, that is a much more complicated issue to troubleshoot. Most likely you need to tell OS X how to send mail via your ISP and give it an account/password. Troubleshooting this is getting my hobby perilously close to my day job! But I will look at it later once the kids have gone to bed.
Tad
Edited to include the following answer:
The Yosemite upgrade re-enabled IPv6, and the google DNS servers were returning an IPv6 answer for the location of smtp.gmail.com. My ISP doesn't support IPv6, so all the connections were failing. Disabling IPv6 in the network control panel, and restarting postfix fixed the problem.
For others venturing down this path, this post explains how to set up postfix to relay mail through gmail:
http://www.anujgakhar.com/2011/12/09/using-macosx-lion-command-line-mail-with-gmail-as-smtp/ and this post adds an additional step for yosemite support:
http://stackoverflow.com/questions/26447316/mac-os-x-10-10-yosemite-postfix-sasl-authentication-failed