eMail (XWiki.sendMessage) defaults to illegal SMTP HELO

SMTP HELO must (according to SMTP spec) be a Domain, (like 'jira.xwiki.org').

Xwiki is defaulting it (if smtp_login is not set) to "XWiki VersionInformation" in XWiki.sendMessage().

Probably it should use InetAddress.getLocalHost().getHostName() for the default domain.

It might not even need the smtp_login configuration, InetAddress.getLocalHost().getHostName() may always be correct for the SMTP HELO.

This was discovered because the Exim4 MTA is smart enough to reject

HELO XWiki version 1.0-beta-5.2310

-Tom