In case I might forget that again: Not only can redirection rules be configured to return a 301 redirect (as of Domino 7.0.3 / 8.0), it is also possible to have web agents return that HTTP status code.
http://www-1.ibm.com/support/docview.wss?uid=sim418e1c9bfb19fb5498525731a00420ba7
The SPR doesn’t say how, but it’s really just straight forward. Example:
Print “Status: 301 Moved Permanently”
Print “Location: http://www.7cars.de/”
Cool.