The news comes on the heels of reports -- still unconfirmed -- that IBM will soon add support for the iPhone to its Lotus Notes enterprise messaging system.

AT&T's new iPhone plans for businesses, which it spelled out on its Web site, come with a minimum two-year service agreement. Unlike its consumer iPhone plans, however, which combine voice and data into one fee, AT&T's business billing splits the two.

Enterprise data plans, for example, start at US$45 monthly for 200 text messages, $55 a month for 1,500 text messages and $65 for unlimited texting. All three plans bundle unlimited domestic data access via AT&T's EDGE network. Consumers' bills, in comparison, break out the 200-message data part of the lowest priced plan as just $20.

Businesses must also sign up for a new voice plan, or have an existing one in place, for each iPhone. Those voice plans are sold at standard corporate rates that range from $39.99 for 450 monthly minutes to $199.99 for 6,000 minutes monthly in plans sans minute sharing among users.

AT&T is also offering a $25 monthly credit to new iPhone accounts activated by March 31; the credit will be applied to bills through the end of 2008.

Last week, reports circulated that IBM would port Lotus Notes to the iPhone, but as of midday Monday, IBM had not made the speculation official with an announcement from its Lotusphere trade show now in progress in Orlando, Florida. On Tuesday, however, IBM is hosting a press conference where it will, according to e-mail from a spokesman on Monday, discuss "new functionality for Lotus Notes/Domino, including new Web 2.0 functionality."

AT&T is the exclusive carrier for the iPhone in the U.S.