TheSerapher/php-mpos — pull request #858 by nicoschtein (2013-11-20 15:22:58+00:00)
Title: Changed sender email field max length

It should be 254 (http://stackoverflow.com/questions/386294/what-is-the-maximum-length-of-a-valid-email-address), but that seems improbable.. so I would go with 50 chars max, instead of 20 that cuts 4 out of 10 emails I receive.
Addresses #856 email field part...