i just want to validate the email in short text question.
where shall i input the validation string? what's the right string shall i input?

i checked again, the same result.

You need to use regexpMatch function for validation_q, it's automatic added to validation.

Denis
manual.limesurvey.org/Expression_Manager#Implemented_Functions

then what's the usage of the validation?
i have read the manual and do it, but you can find the error,i think 50% it's a bug of mailaddress validation

tried all the formula, LS cannot validate email format in EM.