[ietf-dkim] New Issue: ssp-04 DNS operational requirement

[Douglas Otis]

4.3.  ADSP Lookup Procedure
,--
|If a query results in a "SERVFAIL" error response, the algorithm
|terminates without returning a result; possible actions include
|queuing the message or returning an SMTP error indicating a
|temporary failure.
'--
The term "queuing" is rather vague.  In addition SERVFAIL may not be  
visible behind a caching resolver.  In this section it likely to imply  
a message is to be held (as in requeued) pending restoration of DNS  
services, and not that the message is to be queued for delivery to  
individual recipient email-addresses.  This section also imposes a new  
interoperability requirement for SMTP that previously did not exist.   
Prior to the imposition of this requirement, crucial systems with  
addresses assigned within a host address entry could sustain  
communications even in the event of DNS becoming inoperable.

Perhaps the following sentence could be added:
---

To ensure message reception remains viable for crucial systems when  
DNS fails, the IP addresses of crucial SMTP clients should be white- 
listed. This will allow ADSP and DKIM to be selectively bypassed  
during such events.

-Doug