F=d

Never enclose route addresses in <> V8.7 and later

Ordinarily, V8 sendmail forces envelope-sender route addresses[293] to be enclosed in angle brackets. But beginning with V8.7 sendmail, angle brackets can be omitted by specifying F=d.

Under some circumstances, it is possible for these angle-bracketed addresses to be given to a shell, causing them to be wrongly viewed as I/O redirection. This problem is most common with the UUCP and prog delivery agents.

[293] * Also see the DontPruneRoutes option in DontPruneRoutes on page 1024, and how route addresses are handled in rules in Handling Routing Addresses on page 693.

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