Improve handling of errors when sending messages

[clochix]

For now, messages sent from the user often use a wrong send address, displayName-noreply@domain. If the domain is not fully qualified and reachable, lots of email server reject the message. Would it be a privacy concern to use user's email address as the From address ?

If you think there may be privacy concerns, could we add another field in the preferences of the instance, where user can select the from address of this messages, defaulting to displayName-noreply@domain ?

We should also use this address in the reply-to (or sender ? or error-to ? or return path ?) message header, if application doesn't set it, so the rejection message don't get lost in some /dev/null, and users get informed when some message can't be sent.

[ZeHiro]

Maybe it should be nice to have a reconfiguration of postfix when setting the domain (when it is a self hosted instance)

[clochix]

I think we have now a way to distinguish between hosted and self-hosted instances (system env variable HOSTED ?), so we may at least display a link to the documentation on self-hosted instances.

[frankrousseau]

Good idea @clochix

[clochix]

Also see #119 : for now, we have the cozycloud domain hardcoded in some mail options.