agreement
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... (X.400 or RFC 822std11(-> 2822prop)) where there is common agreement on gateway
identification, then this will apply to multiple gateways ...
... Content type not supported 5.6.1 Media unsupp.
1/16 Too many recipients 5.5.3
1/17 No bilateral agreement 5.4.4
1/18 Unsupported critical function 5.3.3 System not capable
...