"If you're in meetings and you come back to your email and you have five minutes between appointments and you have 50 emails, which five messages do you spend your time on in that window of time?" Glotzbach said. Priority Inbox aims to automate that and simplify that decision, he said.
Priority Inbox's functionality is only partially available through third-party client software accessed via POP or IMAP like Outlook. With Priority Inbox activated, an icon appears next to important messages in the inbox of these email software programs, but the message list isn't rearranged, according to Google. "Priority Inbox works best when viewed in Gmail's web [user interface]," a Google spokesman said via email.
The algorithmic calculation that Gmail uses to assign priority includes a variety of parameters, including the frequency with which the user exchanges messages with different senders; the messages that get read and replied to, or, conversely, ignored; and manual indications from users ranking messages as more or less important.
Google provides a variety of options for users to manually customize Priority Inbox settings and preferences if they so choose.
Internal tests at Google showed that people who used Priority Inbox spent on average 6 percent less time managing email, or an entire work-week per year in the case of an employee who normally spends 13 hours per week on email.
"We see this as an ongoing evolution of the focus of Gmail, which has always been around addressing this problem of information overload," Glotzbach said.
Existing Gmail features intended to address this problem include the product's conversation view, which groups together email threads; the search feature, which indexes messages' full text; and its antispam technology.
If the 6 percent time-saving rate holds true for most users, Priority Inbox will be valuable because email will remain as the primary collaboration platform, despite the emergence of tools like shared documents that can be group-edited, said industry analyst Michael Osterman, president of Osterman Research.
"My only concern would be the algorithms that would identify content as important versus less important. This could lead to false positives in which important content is not identified properly," he said. "This is not a serious issue, since nothing will be deleted, but it could lead to delay in accessing important emails."