How should a server process a message stanza of type
'normal', addressed to a bare JID that represents a local user (the scenario of
section 8.5.2.1.1 of RFC 6121) if the corresponding user only has one or more Connected
Resources (but not any Available Resources)?
I think that RFC 6120 §10.5.3.2 covers this:
For a message stanza, if there exists at least one
connected resource for the account then the server SHOULD deliver it to at least one of
the connected resources. If there exists no connected resource then the server MUST either
(a) store the message offline for delivery when the account next has a connected resource
or (b) return a <service-unavailable/> stanza error (Section 8.3.3.19).