Stamps.com Inc. STMP, +1.74% shares plunged more than 35% Thursday afternoon after the company revealed that profit and revenue are expected to hit a huge decline in 2019. The company said in an announcement that it expects earnings to be chopped nearly in half and sales to decline from 2018, without providing specific reasons. Stamps.com reported fourth-quarter profit of $42.7 million, or $2.30 a share, on revenue of $170.2 million, up from $132.5 million a year ago. After adjustments for stock-based compensation and other effects, the company claimed earnings of $3.73 a share, easily beating the average analyst estimate, which called for adjusted earnings of $2.90 a share on sales of $160 million, according to FactSet. For the full year, that gave Stamps.com adjusted earnings of $11.78 a share on revenue of $586.9 million, reflecting growth of 4% and 35% respectively. However, the online mail-supplies company said that adjusted earnings for 2019 are expected to be $5.15 to $6.15 a share on revenue of $540 million to $570 million. Those numbers appear shocking, especially when compared with average analyst estimates of $10.79 a share on revenue of $689.1 million, according to FactSet. The company did not provide any commentary in the release that would explain the forecast, stating executives "plan to discuss certain strategic items during its conference call that impact our business outlook for 2019." The conference call is set for 5 p.m. Eastern time.