Rust
Force Quoted-Printable Encoding for Email

Demonstrates how to force the quoted-printable encoding for email.
Chilkat Rust Downloads

Rust

let email = chilkat::Email::new();

email.set_subject("test");
email.set_from("bob@example.com");
let _ = email.add_to("Mary", "mary@example.com");

// Add plain-text and HTML alternative bodies.
// Include some "=" chars so we can see the quoted-printable encoding when used..
let _ = email.add_plain_text_alternative_body("This is a test == Hello World!");
let _ = email.add_html_alternative_body("<html><body>This is a test == Hello World!</body></html>");

// Examine the MIME of the email to see that it does not use quoted-printable.
// (If the email contained non-usascii chars, it would automatically use quoted-printable.)
let mailman = chilkat::MailMan::new();
println!("{}", mailman.render_to_mime(&email).unwrap_or_default());

// Here is the MIME before forcing quoted-printable.
// Notice the Content-Transfer-Encoding is "7bit" (not "quoted-printable")

// MIME-Version: 1.0
// Date: Tue, 29 Sep 2020 12:26:52 -0500
// Message-ID: <CF274FC0A2F82B98A05B7507DF7DFB966A2C0EB8@CHILKATSLICE>
// Content-Type: multipart/alternative;
//  boundary="------------080901080902080000030208"
// X-Priority: 3 (Normal)
// Subject: test
// From: bob@example.com
// To: Mary <mary@example.com>
// 
// --------------080901080902080000030208
// Content-Transfer-Encoding: 7bit
// Content-Type: text/plain; charset=us-ascii; format=flowed
// 
// This is a test == Hello World!
// --------------080901080902080000030208
// Content-Transfer-Encoding: 7bit
// Content-Type: text/html; charset=us-ascii
// 
// <html><body>This is a test == Hello World!</body></html>
// --------------080901080902080000030208--

println!("----");

// To force quoted-printable, set the Content-Transfer-Encoding header.
// It will automatically propagate as needed to the MIME sub-parts.
email.add_header_field("Content-Transfer-Encoding", "quoted-printable");
println!("{}", mailman.render_to_mime(&email).unwrap_or_default());

// MIME-Version: 1.0
// Date: Tue, 29 Sep 2020 12:26:52 -0500
// Message-ID: <F36B276E3A720FE5111D15CE9142C8909E1F5AB9@CHILKATSLICE>
// Content-Type: multipart/alternative;
//  boundary="------------080901080902080000030208"
// X-Priority: 3 (Normal)
// Subject: test
// From: bob@example.com
// To: Mary <mary@example.com>
// 
// --------------080901080902080000030208
// Content-Transfer-Encoding: quoted-printable
// Content-Type: text/plain; charset=us-ascii; format=flowed
// 
// This is a test =3D=3D Hello World!
// --------------080901080902080000030208
// Content-Transfer-Encoding: quoted-printable
// Content-Type: text/html; charset=us-ascii
// 
// <html><body>This is a test =3D=3D Hello World!</body></html>
// --------------080901080902080000030208--