The current implementation of eluminate allows you to automatically fire a registration tag based on the presence of cm_lm in the querystring. In many cases the registration ID is an email address and it's perfectly sane to also populate the email (2nd) attribute for the tag with the same value.

In the case where cm_lm isn't an email address, the value of cm_lm should only populate the registration ID.

Either check for an email address (contains '@' might be enough), or allow for a new parameter to populate just registration ID (thus preserving behaviour for existing customers) - so email address could be provided separately.

At least note this behaviour in the docs.

A workaround is perfectly feasible, which is what I've done for my current project - but it's not quite as elegant.

// current implementation for reference:
function cmCheckCMEM() {
var b, a, c, d = ["cm_em", "cm_lm", "cm_lm_o"];
for (b = 0; b < d.length; b++) {
c = cmExtractParameter(d[b], document.location.href, true);
if (c) {
if (b == 2) {
cmMakeTag(["tid", "2", "cd_o", c, "em_o", c])
} else {
a = c.indexOf(":");
if (a > -1) {
c = c.substring(a + 1)
}
cmCreateRegistrationTag(c, c)
}
}
}
}