Currently, user cannot modify the subject line in an email that a JAMS reporting job sends. However, a simple job can be created to email a file generated locally or remotely using PowerShell. 

The Send-MailMessage cmdlet can be used to send a simple email with an attachment.

Create a Setup with the reporting job as the first step, and then the email job in the second step.  See the example below as a guide:

$PSEmailServer = "SMTP_Server"
$date = Get-Date -DisplayHint Date
$Time = Get-Date -Format %t
$attachment = "\\ACT2\HelpDesk5\HelpDeskReports\HelpDeskReport*.PDF" 
Send-MailMessage -To name@domain.com -Subject "HelpDesk Report - $Time M - $Date" -From HelpDesk@mvpsi.com -body "Please see attached PDF" -Attachments $attachment

This example will add a date and time stamp to the subject line, and will send all files from the attachment directory.  The user running the job must have access to the remote path.