Change script to look at text file for destination email addresses

I would like to change this script, so that instead of hard coding in the destination email addresses, it will look into a flat txt file and use the email addresses listed in that specific file instead.


###SETUP START###
#-------DO NOT MODIFY-------#
    #Yesterdays Date
        $date = ((Get-Date).AddDays(-2)).ToString("MMM/dd/yyyy")
###SETUP END###

###USER VARIABLES START###
#-------MODIFY AS NEEDED-------#
    #Mail Subject
        $Subject = "Report: "+$date+" REVISED "
    #Body of Email
        $MessageBody = "REVISED - Report for $date. Thank you."
###USER VARIABLES END###

###PROGRAM START###
      # Invokes the Send-MailMessage function to send notification email
Send-MailMessage -From 'email1@mail.com' -To 'email2@mail.com', 'email3@mail.com', 'email4@mail.com' `
  -SmtpServer 'smtp.mail.com' `
  -Subject  $subject `
  -body $MessageBody `
  -BodyAsHtml `
  -Attachment 'C:\Attachment\Attachment.pdf'
 ###PROGRAM END###

Thanks in advance for your assistance