First, @Alan-Kilborn was the one who gave you the expression, not I. He deserves credit.

And I say credit, not blame, because his expression works on the address you just shared.

g.e.n.t.l.e.k.s.dd@gmail.com:444
t.wo…1122334.455.6.6@gmail.com:333
thrifty.wife@yahoo.com:222
cut.3fac.3@yahoo.com:111
b.et.2012.bs.@gmail.com:111

If your expression is not matching that last address, then you have not correctly used Alan’s expression.

b.eth.2012.bs.@gmail.com:111

Here we got 4 dats in email and he’s not deleted.

Alan’s second answer should give the results you requested.

But remember, “be careful what you ask for”: Specifically in this case, be wary of trying to differentiate between spam email and valid email addresses based on number of dots.

• first.mi.last.modifier@gmail.com is valid; there are a lot of “peter jones”-es on gmail, and many of us use middle initials and/or some other modifier after the last name, breaking your “delete if more than three dots” rule
• first.mi.last@alumni.collegename.edu is valid: many colleges give alumni addresses on a subdomain

Anyone who is trying to solve spam by using regex will fail – both by not keeping out enough and by rejecting valid addresses. So if that’s what you’re doing, you might want to go a different direction.,

-—
edit: my examples weren’t right, because re-reading the original post, it looks like you only want to match usernames (before the @ sign) that have more than 3 dots… which is different than I interpreted it (more than three dots anywhere in the email address, before or after the @). I am still leaving the post without deleting it because of conversational context, and because the general warning of my post – don’t expect regex to be able to filter out ‘fake’ email addresses – is still valid.

delete every line containing more then 3 dats

But I gave a solution (above) for “3 or more” dots.

Here’s the semi-obvious slight adjustment to do “more than 3”:

(?-s)^.*?(\..*?){4}@.*\R

Seems like this would match the lines you don’t want. If you can match them you can delete them by replacing with nothing.

(?-s)^.*?(\..*?){3}@.*\R

Use regular expression search mode.