Rust

Enumerate the Header Fields of an Email

Demonstrates the read-only Chilkat Email.NumHeaderFields property together with GetHeaderFieldName and GetHeaderFieldValue to enumerate every header field. Indexing is zero-based, so fields run from 0 to NumHeaderFields - 1. Repeated header fields (a field name that appears more than once) are counted separately. This example builds a small email and prints each header field.

Background: A header field is a single Name: value line at the top of a MIME message. The same field name can legitimately appear multiple times — for example, a message can carry several Received lines, one added by each mail server it passed through. That is why enumerating by index (rather than looking up by name) matters: it lets you see every occurrence in the order it appears.

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Rust

// Demonstrates the read-only Email.NumHeaderFields property and enumerating each
// header field by zero-based index using GetHeaderFieldName and GetHeaderFieldValue.

let email = chilkat::Email::new();
email.set_subject("Header field enumeration");
email.set_from("mary@example.com");
let _ = email.add_to("Joe", "joe@example.com");

let n = email.num_header_fields();
println!("NumHeaderFields = {}", n);

for i in 0..n {
    println!("{}: {}", email.get_header_field_name(i).unwrap_or_default(), email.get_header_field_value(i).unwrap_or_default());
}