Re: [PATCH proxmox 1/1] sendmail: add additional header map

["Shannon Sterz" <s.sterz@proxmox.com>]

On Mon Jun 15, 2026 at 11:20 AM CEST, Nicolas Frey wrote:
> with corresponding methods to add them.
>

generally i like the idea of allowing callers to specify additional
headers, but i wonder if this is a bit too lenient. usually, we try to
handle all encoding and formatting for the caller here, so we can deal
with being in compliance with all rfcs and mail related conventions here
instead of all call-sites.

also this would allow setting headers that are set by proxmox-sendmail
anyway twice. that's probably not ideal either.

so imo, we should either:

* expose at least the formatting helpers here publically so callers can
  use them.
* allow only a limitted set of headers, maybe we an enum. we can then
  handle formatting for the caller be seeing which enum type was
  provided

what do you think?

> this does not check for duplicates for the ones already set by other
> fields/defaults (e.g. To, From, Content-Type, etc.)
>
> Signed-off-by: Nicolas Frey <n.frey@proxmox.com>
> ---
>  proxmox-sendmail/src/lib.rs | 47 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/proxmox-sendmail/src/lib.rs b/proxmox-sendmail/src/lib.rs
> index db751305..355a84c2 100644
> --- a/proxmox-sendmail/src/lib.rs
> +++ b/proxmox-sendmail/src/lib.rs
> @@ -3,6 +3,7 @@
>  //! and alternative html parts to one or multiple receivers via ``sendmail``.
>  //!
>
> +use std::collections::HashMap;
>  use std::io::Write;
>  use std::process::{Command, Stdio};
>
> @@ -247,6 +248,7 @@ pub struct Mail<'a> {
>      attachments: Vec<Attachment<'a>>,
>      mask_participants: bool,
>      noreply: Option<Recipient>,
> +    additional_headers: HashMap<String, String>,
>  }
>
>  impl<'a> Mail<'a> {
> @@ -265,6 +267,7 @@ impl<'a> Mail<'a> {
>              attachments: Vec::new(),
>              mask_participants: true,
>              noreply: None,
> +            additional_headers: HashMap::new(),
>          }
>      }
>
> @@ -393,6 +396,20 @@ impl<'a> Mail<'a> {
>          self
>      }
>
> +    /// Set an arbitrary header to be sent in addition to the default ones already set up by other
> +    /// methods.
> +    pub fn set_header<S: ToString>(&mut self, name: S, body: S) {
> +        self.additional_headers
> +            .insert(name.to_string(), body.to_string());
> +    }
> +
> +    /// Builder-style method to set an arbitrary header in addition to the default ones already
> +    /// set up by other methods.
> +    pub fn with_header<S: ToString>(mut self, name: S, body: S) -> Self {
> +        self.set_header(name, body);
> +        self
> +    }
> +
>      /// Sends the email. This will fail if no recipients have been added.
>      ///
>      /// Note: An `Auto-Submitted: auto-generated` header is added to avoid triggering OOO and
> @@ -584,6 +601,11 @@ impl<'a> Mail<'a> {
>          let rfc2822_date = proxmox_time::epoch_to_rfc2822(now)
>              .with_context(|| "could not convert epoch to rfc2822 date")?;
>          writeln!(header, "Date: {rfc2822_date}")?;
> +
> +        for (name, body) in &self.additional_headers {
> +            writeln!(header, "{name}: {body}")?;
> +        }
> +
>          header.push_str("Auto-Submitted: auto-generated;\n");
>
>          Ok(header)
> @@ -681,6 +703,31 @@ mod test {
>          assert!(result.is_err());
>      }
>
> +    #[test]
> +    fn additional_headers() {
> +        let mail = Mail::new("Sender", "mail@example.com", "hi", "body")
> +            .with_recipient_and_name("Jane Doe", "j.doe@example.com")
> +            .with_header("Reply-To", "mail@example.com")
> +            .with_header("CC", "cc1@example.com,cc2@example.com");
> +        let body = mail.format_mail(0).expect("could not format mail");
> +
> +        assert_lines_equal_ignore_date(
> +            &body,
> +            r#"Subject: hi
> +From: Sender <mail@example.com>
> +To: Jane Doe <j.doe@example.com>
> +Date: Thu, 01 Jan 1970 01:00:00 +0100
> +Reply-To: mail@example.com
> +CC: cc1@example.com,cc2@example.com
> +Auto-Submitted: auto-generated;
> +Content-Type: text/plain;
> +	charset="UTF-8"
> +Content-Transfer-Encoding: 7bit
> +
> +body"#,
> +        )
> +    }
> +
>      #[test]
>      fn simple_ascii_text_mail() {
>          let mail = Mail::new(