It's no secret that Google's mobile team has been slowly rolling out features from its desktop Web mail to the mobile version of its e-mail site. A few weeks ago, visitors to Gmail.com from the iPhone or Android G1 began seeing an option to "mute" a conversation thread, which blocks further messages in the thread from crowding your in-box. Now, another secondary feature has joined muting. On Monday, Google pushed mobile message labeling.
As with muting, being able to organize e-mail messages by color-coded labels like "parties" or "itineraries" can take on new meaning in the restricted space of a cell phone's screen, even one as comparatively large as the iPhone's.
However, this feature is much more restricted on the phone than it is on the desktop. After selecting the message, you can go into "More" options and choose a label from a preexisting category, but you won't be able to create, rename, or delete labels from the phone. As with the mute feature that preceded it, you'll only encounter this restricted label management option from Gmail.com, not from the Android's or iPhone's native in-boxes. This caveat introduces another requirement that will cause many to stick to the phones' other in-boxes for reading Gmail. (You can get around this by creating a bookmarked icon on the home screen.)
If you heavily rely on labels to organize your correspondence, you'll be able to carry that functionality over to your iPhone or G1. Otherwise, the current inability to add labels from the phone means you won't be able to do much unless you first create categories on your desktop.
Labels are available on Android and on the iPhone operating system 2.2.1 or higher, and support U.S. English only.