Abstract: The present invention is directed, in a general aspect, to a nudger for a mixed mail feeder and in particular to an apparatus and method for detecting high stack forces in a stack of mixed mail. The apparatus generally comprises an anti-lean sensor for detecting whether the mailpiece is positioned without improper lean and a stack force sensor for detecting high stack forces at the nudger wall. The method generally comprises the steps of sensing whether the mailpiece is positioned without improper lean and whether the stack of mailpieces is leaning on the nudger wall causing a high stack force which is detrimental to feeding the mailpieces. If high stack forces are present, the apparatus will work to straighten the stack. If the stack does not straighten, the operator is signaled to reorient the stack of mailpieces.