[imp] How to change the greeting text?

[Andreas Semt]

Hello list,

can anybody tell how to change "Welcome to Horde" into "Welcome to 
_my_company_"? In the file /horde/imp/po/de_DE.po (because I am from 
Germany) there are these lines:
---
msgid "Welcome to %s"
msgstr "Willkommen bei %s"
---
Where is %s defined? Sorry, but I am not a PHP hacker. The versions I 
use are: Horde 2.2, IMP 3.2.
A lot of thanks for help!

Best regards,
Andreas