class Net::IMAP::ESearchResult

def max; data.assoc("MAX")&.last end

+IMAP4rev2+ {[RFC9051]}[https://www.rfc-editor.org/rfc/rfc9051.html#section-7.3.4].
Requires +ESEARCH+ {[RFC4731]}[https://www.rfc-editor.org/rfc/rfc4731.html#section-3.1] or

the +MAX+ return option wasn't specified.
Returns +nil+ when the associated search command has no results, or when

The highest message number/UID that satisfies the SEARCH criteria.

:call-seq: max -> integer or nil 
def max;        data.assoc("MAX")&.last        end