function mailadr(id) {
    var domain = "heilpraktikerin-karin-mueller.de";
    var conj = "@";
    var mailadr = "mailto:" + id + conj + domain;
    document.getElementById(id).href=mailadr;
}

function sendmail(id) {
    var domain = "heilpraktikerin-karin-mueller.de";
    var conj = "@";
    var mailadr = "mailto:" + id + conj + domain;
    document.getElementById(id).href=mailadr;
}

// <script type="text/javascript" src="http://www.heilpraktikerin-karin-mueller.de/_mod/sendmail.js"></script>
// <a id="mailid" onClick="javascript:sendmail('mailid');" href="#">Text</a>
// <a name="mailid" onClick="sendto(this)" href="#"> ... </a>

function sendto(a) {
    var domain = "heilpraktikerin-karin-mueller.de";
    var conj = "@";
    var name = a.name;
    var mailadr = "mailto:" + name + conj + domain;
    a.href = mailadr;
}
// <a name="sysadmin" onClick="buildAddress(this,'domain','de')" href="#"> ... </a>
function buildAddress(a,domain,top) {
    var conj = "@";
    var name = a.name;
    var mailaddr = "mailto:" + name + conj + domain + "." + top;
    a.href = mailaddr;
}