XWiki.sendMessage() is sending an illegal argument to HELO, and my very correct Exim4 server is rejecting it when trying to send the registration validation email. The Exception is: com.xpn.xwiki.XWikiException: Error number 10005 in 10: Could not login to mail server 127.0.0.1 port 25 error code 501 (501 Syntactically invalid HELO argument(s) The HELO is: "HELO XWiki version 1.0-beta-5.2310" This is actually illegal according to SMTP specs, it must be a <domain>. Note, this is NOT the "from" address, it is just the SMTP HELO. XWiki.sendMessage() has: if ((login == null) || login.equals("")) login = "XWiki version " + getVersion(); I think it should be: InetAddress.getLocalHost().getHostName(). or settable in XWiki.cfg to the domain you want. In all cases (never login), which, for registration, is not there anyway. -Tom -- May 4, 1970: Alison Krause, Jeffrey Miller, Sandra Scheuer, William Schroeder.