Shares of Research in Motion Ltd., the Canadian maker of the BlackBerry portable e-mail device, sank Friday after the company posted a modest fourth-quarter profit that was below Wall Street forecasts, and offered a first-quarter outlook and subscription figures also below analyst expectations.

The company's shares fell $4.24, or 5 percent, to $80.14 in early trading on the Nasdaq Stock Market. The stock has traded in a 52-week range of $51 to $90.53.

After financial markets closed on Thursday, the company posted a profit of $18.4 million, or 10 cents per share, compared with a net loss of $2.6 million, or one cent per diluted share, a year earlier.

Adjusted earnings, excluding the cost of a patent settlement, related litigation and tax matters, amounted to 65 cents per share. That was in line with RIM's reduced estimates issued on March 3.

Revenue for the three months ending March 4 was $561.2 million, up 39 percent from $404.8 million in the same quarter of last year, but less than the company had originally expected.

Analysts polled by Thomson Financial on average expected the company to earn 67 cents per share on $567.19 million in revenue.

RIM's growth was curtailed by the high-profile and protracted patent dispute with Richmond, Va.-based NTP Inc., which was settled just before the quarter ended.

The company said it added about 625,000 new BlackBerry subscriber accounts during the quarter, giving it about 4.9 million subscribers at the end of the quarter.

The company said it expects first-quarter 2007 earnings to be 60 cents to 65 cents per share, or 62 cents to 67 cents per share excluding extraordinary charges and expenses. The company expects quarterly revenue from $580 to $610 million.

Analysts are looking for earnings of 76 cents per share on $625.6 million in revenue.

Andrew J. Neff, an analyst at Bear Stearns, said in a note he was concerned "that the wireless e-mail market could be saturating at current levels, requiring new products/marketing methods to jumpstart growth. ... While potential for wireless e-mail may be very large, the issue is what price of service/handset is required to rejuvenate growth."

He downgraded the stock from "Peer Perform" to "Underperform" to reflect slow growth, he said.

Goldman Sachs analyst Brantley Thompson, on the other hand, maintained his "Outperform" rating based on a continued strong mobile e-mail market, and subscribers' brand loyalty to the BlackBerry.

"We believe that RIM's barriers to competitors are formidable as was proven by the fact that every major RIM customer recently tested the major competitors under the threat that RIM would be shut down, and the net impact was a little if any loss of customers," he said.

He added that new product launches and expansion into Asia could also help the company.