$ perl -wE 'q{Even more test address@test.com @20} =~ /[^@\n]*(?:\S@[^@\n]*)*/ and say $&'
Even more test address
$ perl -wE 'q{Even more test address@test.com @20} =~ /[^@\n]*(?:\S@[^@\n]*)+/ and say $&'
Even more test address@test.com