You can also use this solution for Lotus Notes to iPhone...
"WirelessMail for Notes" (
http://martinscott.com/wirelessmail) will push-redirect copies of Lotus Notes email to any other email address you specify, such as a Yahoo or GMail account. Then the iPhone can get it directly from there. The emails in your Inbox will show up in the iPhone inbox automatically, appearing to be sent from the original sender, including the other names in the cc and sendto lists.
There is nothing to install on the server or on the iPhone; you install WirelessMail to your mailfile through the installer. Yet you don't have to leave your computer on; it runs as an agent in your mailfile on the server.
There's a 30 day free trial, and it installs easily as long as you have at least "Designer" level access to your mail box. Most users do, but if you don't, your email administrator can install it for you.
One problem currently with iPhone (using any email solution) is that replies you send from the iPhone will appear to come from your Yahoo/gmail account. This is unlike other handhelds let you change the From address to that of your corporate email. I've heard a lot of complaints about this, and trust that Apple is listening and will address in an over-the-air fix for the iPhone.
Another more direct way available in some organizations is to set the iPhone's IMAP settings to get mail directly from the Domino mail server, if the IMAP server task is running on that server. However, some organizations don't like to leave this running. Most don't.