Can I make a suggestion.

When we 
add an extra field in the table 'vacation' like  "email_name" and make adjusable in vacation.php / vacatin.tpl

workflow:

First time that an 
"out of office" for an email address  is created 
mailname is created from $email and $name from table 'mailbox'
display it in the template.

With this in (vacation.php / vacatin.tpl) adaptable to the admin or user [1] customize it at your own discretion. eg
<DO NOT REPLY> noreply@domein.org or leave it unchanged

It is therefore also useable if there would be a change in using a other module than vacation.pl


[1]
with "user control" you would be close to the user.

$ add_realname also comes in this config.inc.php

it's all just an idea but would love to hear your opinion

regards Jan Kruis