Added property to define an optional image host to prevent a certain class of Cross-Site-Scripting attacks. The property allows to specify a separate domain that is used in constructing image URLs.

File '' is enhanced by property com.openexchange.mail.imageHost. Default is empty; no image host used.

Exemplary setup:
- Artificially add a host name to /etc/hosts:
- Enable the com.openexchange.mail.imageHost property in
- Check a mail with an inline image