Use sed to remove \r characters:
echo -e "$releasenotes" | sed 's/\r//' | mail -s "$ALERT_EMAIL_SUBJECT" "$ALERT_EMAIL_ADDR"
losing line endings using Linux mail sending email to Windows Outlook
Use sed to remove \r characters:
echo -e "$releasenotes" | sed 's/\r//' | mail -s "$ALERT_EMAIL_SUBJECT" "$ALERT_EMAIL_ADDR"