HTML5 has a multiple attribute that can be specified for e-mail addresses as well as files. For e-mail, it would be a set of comma-separated strings, each of which is a valid email address.

When applying the multiple attribute to the existing jQuery Validation Plugin Demo, more than one e-mail address will not validate.

There are solutions to this (e.g., http://stackoverflow.com/questions/10352221/jquery-validation-plugin-multiple-email-addresses), but ideally, one should be able to write the following without using addMethod:

<input id="email1" name="email1" type="email" multiple>