In the SMTP RCPT command, sendmail is required
to express the recipient's address relative to the
local host. For domain addresses, this simply means that the address
should be RFC2821-compliant.
The -d12.1 (a.k.a. -d12)
debugging switch causes sendmail to print the
address as it appeared before it was made relative:
If the addr is for the sender or recipient and
is being processed from a queue file, nothing more is printed, and
the addr is processed by
canonify rule set 3. If the delivery agent for the
recipient has the F=C flag set (F=C) and the recipient address lacks a domain
part, the domain of the sender is appended, and the result is
processed by the canonify rule set 3 again.
Sender/recipient-specific rule sets are then applied
(1 and S= for the sender, or
2 and R= for the recipient).
Next, the final rule set 4 is applied, and any
sendmail macros in the result are expanded.
Finally, the fully qualified and relative address is printed as:
remotename => `addr'