** Shares of shipping and mailing firm Pitney Bowes PBI.N jump 12% to $12.3, hitting their highest since Jan 2021
** Stock on track for its biggest single-day percentage gain since late January, if gains hold
** More than 4 mln shares exchanged hands on Monday, which is about 17 times its 25-DMA, according to data compiled by LSEG
** PBI's short interest stands at 7.4% of free float, with short sellers' on paper losses at $18.6 mln at a price of $12.52 - Ortex data
** Including sessions' gains, PBI up more than 70% YTD
(Reporting by Shashwat Chauhan in Bengaluru)
((Shashwat.Chauhan@thomsonreuters.com))