I want to extract email:pass from every line to be like this

@PeterJones had the right idea, it’s always difficult when not actually able to test a solution and in this case his will actually erase both user and email fields.
Instead try
Find What:(?-s)^.*?:(.+\R?)
Replace With:\1

As it’s a regular expression you must have the search mode set to regular expression.

Terry

I am on my phone, so cannot verify, but it would be something like ^.*?: and replace with nothing, in regular expression mode

(This means search from beginning of the line and any characters up to and including the first colon, and replace with nothing. The Read This Post First and FAQ section will provide links to more info on regular expression search/replace)