There usually isn't much point in sending pictures large than your recipient's monitor resolution; even 1024 x 768 is satisfactory. For most casual email purposes, photos files can be reduced to around 500kb or less without loss of 'quality'. A photo editing program can do this, or it should be able be done after tagging the photo(s), right clicking on the group thus selected, and select "send to" / email recipient. A menu should then be offered which allow selection of a number of size options to which each picture might be reduced.
I've described what is possible with a Windows / Firefox combination; I would be surprised if the MS alternative didn't offer the same path in some form or another...