mod_s2s_keepalive: Ignore errors from the local server If a stanza can't be delivered and instead an bounce is generated, the origin of the error, when different from the stanza 'from' should be indicated in the 'by' attribute of the <error>, which we look for here so this doesn't count as a successful ping. An error that does come from the remote means we have connectivity, but probably no XEP-0199 handling. This is fine. We care about connectivity, not protocol.

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summary: Block s2s connections based on admin blocklists
...

This module uses the blocklists set by admins for blocking s2s
connections.

So if an admin blocks a bare domain using [Blocking Command][xep191]
via [mod\_blocklist][doc:modules:mod_blocklist] then no s2s connections
will be allowed to or from that domain.