When realnames are used, they are sometimes longer than 14 chars and by an inaccurate formatting in email_api.php this destroys the formating of the history in emails, because there is then no blank.

email_api.php
[...]

[...]

$t_message .=   str_pad( date( t_normal_date_format, t_raw_history_item['date'] ), 16 ) .

str_pad( t_raw_history_item['username'], 15 ) .

[...]

suggestion:
                    str_pad( t_raw_history_item['username'], 14 ) . ' ' .
or even better: a little more space in case 'show_realname' is ON.