obfuscate email address in logs
in some logs, the clients logs full headers if there are errors, i.e. in https://leap.se/code/issues/4838#note-2
this makes me uneasy submitting bugreports.
at the very least, email addresses should even
- obfuscated so they cannot get gathered by spambots or
- there should be an options to strip them out completely
(from redmine: created on 2013-12-23, relates #4838 (closed), relates #5403 (closed))