Hello @darrinh
That error shown doesn’t real tell much, other then you have a issue.
Example of mine, which looks like yours.
transport_email_enabled = true
transport_email_hostname = localhost
transport_email_port = 25
transport_email_subject_prefix = [graylog]
transport_email_from_email = root@domain.com
Make sure your email software is working, send test mail.
https://clients.javapipe.com/knowledgebase/132/How-to-Test-Sendmail-From-Command-Line-on-Linux.html
To help further we would need more information. A better understanding on what is needed please take a look here.