What does (?i) and ?@ in this regex mean [duplicate]

Answer 1

? here is the UNGREEDY or LAZYNESS modifier:

.*?

It means: "everything is good until the @ character that follows is detected". Otherwise .* would match everything until the end of the string.

Read about it here: http://www.regular-expressions.info/repeat.html

Answer 2

demo here : https://regex101.com/r/hE9gB4/1

(?i)<.*?@(?P<domain>\w+\.\w+)(?=>)

its actually getting your domain name from the email id:

(?i) makes it match case insensitive and

?@ is nothing but @ which matches the character @ literally.

the ? in your ?@ is part of .*? which we call as a lazy operator, It will give you the text between the < and @

if you dont use the ? after the .* it will match everything after < to the end. ( we call this as the greedy operator)