It has come to my attention that there are actual human beings who think that the plural of “email” is “email.”

These people are sociopaths.

You can use “email” as a collective– “I get lots of email” or “I sent some email” if you like, but if it is used as a plural, ie, “He sent two emails”, and you don’t include that -s at the end, you are bad and wrong and you should go far away.

Or embrace the phrase “email messages,” and dodge the issue that way.

The end.