It is demonstrated that detailed information can be gained on the inelastic mechanism of correlated electron transfer through a molecular wire if one analyses the current behavior in dependence on the strength of the external electric field. The approach is complementary to the derivation of the current-voltage characteristics, and the given analysis of the current-length effect observed at a fixed electric field-strength allows to specify the influence of the blocking transmission factor on incoherent electron transfer. It is found that at small external electric field-strength the current through a regular molecular wire exhibits an Ohmic behaviour while at strong fields electron-electron correlations lead to an exponential decrease of the current.