jku001@schuldiner:/tmp$ set -x
jku001@schuldiner:/tmp$ egrep [\+] test.txt
+ egrep --color=auto '[+]' test.txt
user+bla@me.com
+user@test.nl
jku001@schuldiner:/tmp$ egrep '+' test.txt
+ egrep --color=auto + test.txt
user+bla@me.com
+user@test.nl
me@you.info
whatever@example.com
bla[@you.de
whoops]@where.com

jku001@schuldiner:/tmp$