Specifies the maximum E-value for a hit. See accept options,
An expectation value (E-value) is the expected number
of local alignments with a given score that would be found in random sequences
of the same length as the query and database. This is a convenient way to
express how likely it is that a given alignment is due to an evolutionary
relationship rather than chance similarity.
For local alignments only; E-values
cannot be computed for global alignments.