# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?:\.|\+.*)(?=.*?@gmail\.com)//g;t' <<< "n.fl.jersey.s@gmail.com
nfl.jerseys@gmail.com
n.flj.er.se.ys@gmail.com
foo+bar@gmail.com
"
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 SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html