Shares of Stamps.com Inc. jumped 20 percent on Friday after the online postal services provider reported strong third-quarter results and raised its full-year guidance. But IPC the Hospitalist Co. Inc. saw its shares drop 17 percent after announcing results that were less than expected and providing a more pessimistic outlook.

Stamps.com of El Segundo reported net income of $7 million (42 cents a share), compared with $4.5 million (30 cents) in the same period a year earlier. Revenue rose 17 percent to $29.1 million, with gains in business from enterprise customers, small businesses and customers with high shipping volumes.

Excluding one-time costs, net income was 50 cents a share. Analysts surveyed by FactSet expected adjusted net income of 38 cents a share on revenue of $28.4 million.

For the full year, Stamps.com Inc. now expects adjusted net income of $1.55 to $1.75 a share on revenue of $110 million to $120 million. That’s up from previous guidance of $1.35 to $1.55 a share profit, and $107 million to $117 million in revenue.

IPC of North Hollywood operates hospital-based physician practices in 28 states. It reported 21 percent higher net income of $7.8 million (46 cents), compared with $6.5 million (38 cents) in the same period a year earlier. Revenue rose 12 percent to more than $127 million

The Wall Street consensus was for higher net income of 49 cents a share on revenue of $130 million.

IPC lowered its full-year guidance. The company now expects full-year profit of $1.88 to $1.92 a share, down from $1.96 to $2.06.

In Nasdaq trading, Stamps share closed up $4.40, or 20 percent, to $26.20.

IPC shares closed down $7.07, or 17 percent, to $34.83.