Rust

Get a Header Attribute of an Attached Message

Demonstrates the Chilkat Email.GetAttachedMessageAttr method, which returns a header-field attribute value for the Nth attached (embedded) email. The first argument is the zero-based attached-message index, the second is the header field name, and the third is the attribute name. This example attaches an email and reads the filename attribute of its Content-Disposition header.

Background: MIME header fields can carry named attributes (parameters) after the main value — for example Content-Disposition: attachment; filename="report.eml", where filename is an attribute. Rather than parsing the raw header yourself, this method extracts a single named attribute from a chosen header of a specific embedded message, which is convenient when a message forwards other emails as nested message/rfc822 parts.

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// Demonstrates the GetAttachedMessageAttr method, which returns a header-field attribute
// value for the Nth attached (embedded) email.  The first argument is the zero-based
// attached-message index, the second is the header field name, and the third is the attribute name.

// Build an inner email to attach.
let inner_email = chilkat::Email::new();
inner_email.set_subject("Embedded message");
inner_email.set_from("alice@example.com");
let _ = inner_email.add_to("Bob", "bob@example.com");

// Attach it to an outer email as a message/rfc822 part.
let email = chilkat::Email::new();
email.set_subject("Has an attached message");
if email.attach_email(&inner_email).is_err() {
    println!("{}", email.last_error_text());
    return;
}

// Get the "filename" attribute of the "Content-Disposition" header of the first
// attached message (index 0).
let fname = email.get_attached_message_attr(0, "Content-Disposition", "filename").unwrap_or_default();
println!("Attached message filename attribute: {}", fname);