<match **>
type mail
host smtp.gmail.com
port 587
domain gmail.com
from SOURCE
to DEST1,DEST2,DEST3
subject SUBJECT
user USERNAME( ex. hoge@gmail.com)
password xxxxxx
enable_starttls_auto true
enable_tls false
out_keys tag,foo,message
time_locale UTC
</match>
</ROOT>
Fluentd 0.12.13 or later supports secret parameter feature. https://github.com/fluent/fluentd/blob/4e3a4ecb/ChangeLog#L34
This feature works as below: