re = /^([^\s\@])+\@(([^\s\@\.])+\.)+([^\s\.]{2,})+$/mi
str = 'test@rws.lt
res+ds@gmail.com
res-dsaf@f.com
4334-@fdf.fdsfdsfdsfs.dfsd
e@ds.lt
w.w@f.lt
w--w--we@d.lr
we@rer-rer.lt
wee@we.co.uk
mindaugas.dsd@dsfs.com
c@c.com
xn--iema-kbbc.lt@xn--iema-kbbc.lt
"Joe.\\\\Blow"@example.com
bc.123@example.com
reŠna@g.com
квіточка@пошта.укр
"Fred\\ Bloggs"@example.com
dsad@dfs.c
ewr@rsrew@dsad.com
@gf.com
ree+er@.com
res@.lt
@.lt
res.lt
sad@
s@fdf..com
es@fdf..com
w@fdsf.
'
subst = ''
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html