512369f93e 2026-08-01 1: //! SMTP server implementation for receiving and processing emails.
512369f93e 2026-08-01 2: //!
512369f93e 2026-08-01 3: //! This module handles SMTP connections, email parsing, and forwarding to
512369f93e 2026-08-01 4: //! Telegram.
512369f93e 2026-08-01 5:
f5ed284f8c 2025-06-21 6: use crate::{
f5ed284f8c 2025-06-21 7: Cursor,
0f47e23e21 2026-01-12 8: telegram::TelegramTransport,
f5ed284f8c 2025-06-21 9: utils::{
f5ed284f8c 2025-06-21 10: Attachment,
f5ed284f8c 2025-06-21 11: RE_DOMAIN,
0f47e23e21 2026-01-12 12: validate,
f5ed284f8c 2025-06-21 13: },
f5ed284f8c 2025-06-21 14: };
f5ed284f8c 2025-06-21 15:
f5ed284f8c 2025-06-21 16: use std::{
f5ed284f8c 2025-06-21 17: collections::{
f5ed284f8c 2025-06-21 18: HashMap,
f5ed284f8c 2025-06-21 19: HashSet,
f5ed284f8c 2025-06-21 20: },
f5ed284f8c 2025-06-21 21: io::Error,
072229b5bf 2026-01-01 22: sync::Arc,
f5ed284f8c 2025-06-21 23: };
f5ed284f8c 2025-06-21 24:
14ef340959 2026-01-01 25: use async_compat::Compat;
f5ed284f8c 2025-06-21 26: use mailin_embedded::{
f5ed284f8c 2025-06-21 27: Response,
f5ed284f8c 2025-06-21 28: response::{
f5ed284f8c 2025-06-21 29: INTERNAL_ERROR,
f5ed284f8c 2025-06-21 30: INVALID_CREDENTIALS,
f5ed284f8c 2025-06-21 31: NO_MAILBOX,
f5ed284f8c 2025-06-21 32: OK
f5ed284f8c 2025-06-21 33: },
f5ed284f8c 2025-06-21 34: };
f5ed284f8c 2025-06-21 35: use regex::{
f5ed284f8c 2025-06-21 36: Regex,
f5ed284f8c 2025-06-21 37: escape,
a044f68fa7 2025-08-23 38: };
a044f68fa7 2025-08-23 39: use stacked_errors::{
a044f68fa7 2025-08-23 40: Result,
a044f68fa7 2025-08-23 41: StackableErr,
a044f68fa7 2025-08-23 42: bail,
f5ed284f8c 2025-06-21 43: };
f5ed284f8c 2025-06-21 44: use tgbot::types::ChatPeerId;
f5ed284f8c 2025-06-21 45:
f5ed284f8c 2025-06-21 46: /// `SomeHeaders` object to store data through SMTP session
f5ed284f8c 2025-06-21 47: #[derive(Clone, Debug)]
f5ed284f8c 2025-06-21 48: struct SomeHeaders {
f5ed284f8c 2025-06-21 49: from: String,
f5ed284f8c 2025-06-21 50: to: Vec<String>,
f5ed284f8c 2025-06-21 51: }
f5ed284f8c 2025-06-21 52:
f5ed284f8c 2025-06-21 53: /// `MailServer` Central object with TG api and configuration
f5ed284f8c 2025-06-21 54: #[derive(Clone, Debug)]
f5ed284f8c 2025-06-21 55: pub struct MailServer {
f5ed284f8c 2025-06-21 56: data: Vec<u8>,
f5ed284f8c 2025-06-21 57: headers: Option<SomeHeaders>,
f5ed284f8c 2025-06-21 58: relay: bool,
f5ed284f8c 2025-06-21 59: tg: Arc<TelegramTransport>,
f5ed284f8c 2025-06-21 60: fields: HashSet<String>,
f5ed284f8c 2025-06-21 61: address: Regex,
f5ed284f8c 2025-06-21 62: }
f5ed284f8c 2025-06-21 63:
f5ed284f8c 2025-06-21 64: impl MailServer {
1723b63d69 2026-08-01 65: /// Initializes the mail server: sets up the Telegram API client and
1723b63d69 2026-08-01 66: /// validates all required configuration values.
512369f93e 2026-08-01 67: ///
1723b63d69 2026-08-01 68: /// # Arguments
1723b63d69 2026-08-01 69: /// * `settings` - Parsed application configuration.
512369f93e 2026-08-01 70: ///
512369f93e 2026-08-01 71: /// # Errors
1723b63d69 2026-08-01 72: /// Returns an error if required configuration values are missing or invalid.
512369f93e 2026-08-01 73: /// server fails to start.
1723b63d69 2026-08-01 74: pub fn new (settings: config::Config) -> Result<MailServer> {
f5ed284f8c 2025-06-21 75: let api_key = settings.get_string("api_key")
f5ed284f8c 2025-06-21 76: .context("[smtp2tg.toml] missing \"api_key\" parameter.\n")?;
f5ed284f8c 2025-06-21 77: let mut recipients = HashMap::new();
f5ed284f8c 2025-06-21 78: for (name, value) in settings.get_table("recipients")
f5ed284f8c 2025-06-21 79: .expect("[smtp2tg.toml] missing table \"recipients\".\n")
f5ed284f8c 2025-06-21 80: {
f5ed284f8c 2025-06-21 81: let value = value.into_int()
f5ed284f8c 2025-06-21 82: .context("[smtp2tg.toml] \"recipient\" table values should be integers.\n")?;
f5ed284f8c 2025-06-21 83: recipients.insert(name, value);
f5ed284f8c 2025-06-21 84: }
f5ed284f8c 2025-06-21 85:
14ef340959 2026-01-01 86: let tg = Arc::new(TelegramTransport::new(api_key, recipients, &settings)?);
f5ed284f8c 2025-06-21 87: let fields = HashSet::<String>::from_iter(settings.get_array("fields")
f5ed284f8c 2025-06-21 88: .expect("[smtp2tg.toml] \"fields\" should be an array")
f5ed284f8c 2025-06-21 89: .iter().map(|x| x.clone().into_string().expect("should be strings")));
f5ed284f8c 2025-06-21 90: let mut domains: HashSet<String> = HashSet::new();
a044f68fa7 2025-08-23 91: let extra_domains = settings.get_array("domains").stack()?;
f5ed284f8c 2025-06-21 92: for domain in extra_domains {
f5ed284f8c 2025-06-21 93: let domain = domain.to_string().to_lowercase();
f5ed284f8c 2025-06-21 94: if RE_DOMAIN.is_match(&domain) {
f5ed284f8c 2025-06-21 95: domains.insert(domain);
f5ed284f8c 2025-06-21 96: } else {
f5ed284f8c 2025-06-21 97: panic!("[smtp2tg.toml] can't check of domains in \"domains\": {domain}");
f5ed284f8c 2025-06-21 98: }
f5ed284f8c 2025-06-21 99: }
f5ed284f8c 2025-06-21 100: let domains = domains.into_iter().map(|s| escape(&s))
f5ed284f8c 2025-06-21 101: .collect::<Vec<String>>().join("|");
f748e99b70 2026-08-01 102: let address = Regex::new(&format!("^[a-z0-9][-a-z0-9]*(@({domains}))?$")).stack()?;
f5ed284f8c 2025-06-21 103: let relay = match settings.get_string("unknown")
f5ed284f8c 2025-06-21 104: .context("[smtp2tg.toml] can't get \"unknown\" policy.\n")?.as_str()
f5ed284f8c 2025-06-21 105: {
f5ed284f8c 2025-06-21 106: "relay" => true,
f5ed284f8c 2025-06-21 107: "deny" => false,
f5ed284f8c 2025-06-21 108: _ => {
f5ed284f8c 2025-06-21 109: bail!("[smtp2tg.toml] \"unknown\" should be either \"relay\" or \"deny\".\n");
f5ed284f8c 2025-06-21 110: },
f5ed284f8c 2025-06-21 111: };
f5ed284f8c 2025-06-21 112:
f5ed284f8c 2025-06-21 113: Ok(MailServer {
f5ed284f8c 2025-06-21 114: data: vec!(),
f5ed284f8c 2025-06-21 115: headers: None,
f5ed284f8c 2025-06-21 116: relay,
f5ed284f8c 2025-06-21 117: tg,
f5ed284f8c 2025-06-21 118: fields,
f5ed284f8c 2025-06-21 119: address,
f5ed284f8c 2025-06-21 120: })
f5ed284f8c 2025-06-21 121: }
f5ed284f8c 2025-06-21 122:
512369f93e 2026-08-01 123: /// Retrieves the Telegram chat ID for a given email address, checks that
512369f93e 2026-08-01 124: /// used domain is allowed.
512369f93e 2026-08-01 125: ///
512369f93e 2026-08-01 126: /// # Arguments
1723b63d69 2026-08-01 127: /// * `name` - Email address or username to look up.
512369f93e 2026-08-01 128: ///
512369f93e 2026-08-01 129: /// # Returns
512369f93e 2026-08-01 130: /// * `Result<ChatPeerId>` - Telegram chat ID for the address, or default if
512369f93e 2026-08-01 131: /// not found.
f748e99b70 2026-08-01 132: pub fn get_id (&self, name: &str) -> Result<&ChatPeerId> {
f748e99b70 2026-08-01 133: if self.address.is_match(name) {
1723b63d69 2026-08-01 134: Ok(self.tg.get(name).unwrap_or(&self.tg.default))
f748e99b70 2026-08-01 135: } else {
f748e99b70 2026-08-01 136: bail!("Doesn't look like address from one of our domains.");
f5ed284f8c 2025-06-21 137: }
f5ed284f8c 2025-06-21 138: }
f5ed284f8c 2025-06-21 139:
f5ed284f8c 2025-06-21 140: /// Attempt to deliver one message
f5ed284f8c 2025-06-21 141: async fn relay_mail (&self) -> Result<()> {
f5ed284f8c 2025-06-21 142: if let Some(headers) = &self.headers {
f5ed284f8c 2025-06-21 143: let mail = mail_parser::MessageParser::new().parse(&self.data)
f5ed284f8c 2025-06-21 144: .context("Failed to parse mail.")?;
f5ed284f8c 2025-06-21 145:
f5ed284f8c 2025-06-21 146: // Adding all known addresses to recipient list, for anyone else adding default
f5ed284f8c 2025-06-21 147: // Also if list is empty also adding default
f5ed284f8c 2025-06-21 148: let mut rcpt: HashSet<&ChatPeerId> = HashSet::new();
f5ed284f8c 2025-06-21 149: if headers.to.is_empty() && !self.relay {
f5ed284f8c 2025-06-21 150: bail!("Relaying is disabled, and there's no destination address");
f5ed284f8c 2025-06-21 151: }
f5ed284f8c 2025-06-21 152: for item in &headers.to {
f5ed284f8c 2025-06-21 153: rcpt.insert(self.get_id(item)?);
f5ed284f8c 2025-06-21 154: };
f5ed284f8c 2025-06-21 155: if rcpt.is_empty() {
f5ed284f8c 2025-06-21 156: self.tg.debug("No recipient or envelope address.").await?;
f5ed284f8c 2025-06-21 157: rcpt.insert(&self.tg.default);
f5ed284f8c 2025-06-21 158: };
f5ed284f8c 2025-06-21 159:
0f47e23e21 2026-01-12 160: // preparing message header
0f47e23e21 2026-01-12 161: let mut reply: Vec<String> = vec!["<blockquote expandable>".into()];
f5ed284f8c 2025-06-21 162: if self.fields.contains("subject") {
f5ed284f8c 2025-06-21 163: if let Some(subject) = mail.subject() {
0f47e23e21 2026-01-12 164: reply.push(format!("<u><i>Subject:</i></u> <code>{}</code>", validate(subject).stack()?));
f5ed284f8c 2025-06-21 165: } else if let Some(thread) = mail.thread_name() {
0f47e23e21 2026-01-12 166: reply.push(format!("<u><i>Thread:</i></u> <code>{}</code>", validate(thread).stack()?));
f5ed284f8c 2025-06-21 167: }
f5ed284f8c 2025-06-21 168: }
f5ed284f8c 2025-06-21 169: // do we need to replace spaces here?
f5ed284f8c 2025-06-21 170: if self.fields.contains("from") {
0f47e23e21 2026-01-12 171: reply.push(format!("<u><i>From:</i></u> <code>{}</code>", validate(&headers.from).stack()?));
0f47e23e21 2026-01-12 172: }
0f47e23e21 2026-01-12 173: if self.fields.contains("date")
0f47e23e21 2026-01-12 174: && let Some(date) = mail.date()
0f47e23e21 2026-01-12 175: {
0f47e23e21 2026-01-12 176: reply.push(format!("<u><i>Date:</i></u> <code>{date}</code>"));
0f47e23e21 2026-01-12 177: }
0f47e23e21 2026-01-12 178: reply.push("</blockquote><pre>".into());
c996f5c871 2026-01-12 179: let reply = reply.join("\n");
f5ed284f8c 2025-06-21 180:
f5ed284f8c 2025-06-21 181: let html_parts = mail.html_body_count();
f5ed284f8c 2025-06-21 182: let text_parts = mail.text_body_count();
f5ed284f8c 2025-06-21 183: let attachments = mail.attachment_count();
f5ed284f8c 2025-06-21 184: if html_parts != text_parts {
f5ed284f8c 2025-06-21 185: self.tg.debug(&format!("Hm, we have {html_parts} HTML parts and {text_parts} text parts.")).await?;
f5ed284f8c 2025-06-21 186: }
f5ed284f8c 2025-06-21 187: //let mut html_num = 0;
f5ed284f8c 2025-06-21 188: let mut text_num = 0;
f5ed284f8c 2025-06-21 189: let mut file_num = 0;
f5ed284f8c 2025-06-21 190: // let's display first html or text part as body
c996f5c871 2026-01-12 191: let mut body: String = "".into();
f5ed284f8c 2025-06-21 192: /*
f5ed284f8c 2025-06-21 193: * actually I don't wanna parse that html stuff
f5ed284f8c 2025-06-21 194: if html_parts > 0 {
a044f68fa7 2025-08-23 195: let text = mail.body_html(0).stack()?;
f5ed284f8c 2025-06-21 196: if text.len() < 4096 - header_size {
f5ed284f8c 2025-06-21 197: body = text;
f5ed284f8c 2025-06-21 198: html_num = 1;
f5ed284f8c 2025-06-21 199: }
f5ed284f8c 2025-06-21 200: };
f5ed284f8c 2025-06-21 201: */
f5ed284f8c 2025-06-21 202: if body.is_empty() && text_parts > 0 {
f5ed284f8c 2025-06-21 203: let text = mail.body_text(0)
c996f5c871 2026-01-12 204: .context("Failed to extract text from message")?
c996f5c871 2026-01-12 205: .replace("\r\n", "\n");
db04f7359b 2026-01-18 206: let text = validate(&text).stack()?;
c996f5c871 2026-01-12 207: // 6:
c996f5c871 2026-01-12 208: // - (headers)
0f47e23e21 2026-01-12 209: // - (mail text)
0f47e23e21 2026-01-12 210: // - 6: </pre>
6ce625a569 2026-01-12 211: if text.len() < 4096 - ( reply.len() + 6 ) {
db04f7359b 2026-01-18 212: body = text.to_string();
f5ed284f8c 2025-06-21 213: text_num = 1;
f5ed284f8c 2025-06-21 214: }
f5ed284f8c 2025-06-21 215: };
db04f7359b 2026-01-18 216: let msg = format!("{}{}</pre>", reply, body);
f5ed284f8c 2025-06-21 217:
f5ed284f8c 2025-06-21 218: // and let's collect all other attachment parts
f5ed284f8c 2025-06-21 219: let mut files_to_send = vec![];
f5ed284f8c 2025-06-21 220: /*
f5ed284f8c 2025-06-21 221: * let's just skip html parts for now, they just duplicate text?
f5ed284f8c 2025-06-21 222: while html_num < html_parts {
a044f68fa7 2025-08-23 223: files_to_send.push(mail.html_part(html_num).stack()?);
f5ed284f8c 2025-06-21 224: html_num += 1;
f5ed284f8c 2025-06-21 225: }
f5ed284f8c 2025-06-21 226: */
f5ed284f8c 2025-06-21 227: while text_num < text_parts {
a044f68fa7 2025-08-23 228: files_to_send.push(mail.text_part(text_num.try_into().stack()?)
f5ed284f8c 2025-06-21 229: .context("Failed to get text part from message.")?);
f5ed284f8c 2025-06-21 230: text_num += 1;
f5ed284f8c 2025-06-21 231: }
f5ed284f8c 2025-06-21 232: while file_num < attachments {
a044f68fa7 2025-08-23 233: files_to_send.push(mail.attachment(file_num.try_into().stack()?)
f5ed284f8c 2025-06-21 234: .context("Failed to get file part from message.")?);
f5ed284f8c 2025-06-21 235: file_num += 1;
f5ed284f8c 2025-06-21 236: }
f5ed284f8c 2025-06-21 237:
f5ed284f8c 2025-06-21 238: for chat in rcpt {
f5ed284f8c 2025-06-21 239: if !files_to_send.is_empty() {
f5ed284f8c 2025-06-21 240: let mut files = vec![];
f5ed284f8c 2025-06-21 241: // let mut first_one = true;
f5ed284f8c 2025-06-21 242: for chunk in &files_to_send {
f5ed284f8c 2025-06-21 243: let data: Vec<u8> = chunk.contents().to_vec();
f5ed284f8c 2025-06-21 244: let mut filename: Option<String> = None;
f5ed284f8c 2025-06-21 245: for header in chunk.headers() {
f5ed284f8c 2025-06-21 246: if header.name() == "Content-Type" {
f5ed284f8c 2025-06-21 247: match header.value() {
f5ed284f8c 2025-06-21 248: mail_parser::HeaderValue::ContentType(contenttype) => {
f5ed284f8c 2025-06-21 249: if let Some(fname) = contenttype.attribute("name") {
f5ed284f8c 2025-06-21 250: filename = Some(fname.to_owned());
f5ed284f8c 2025-06-21 251: }
f5ed284f8c 2025-06-21 252: },
f5ed284f8c 2025-06-21 253: _ => {
f5ed284f8c 2025-06-21 254: self.tg.debug("Attachment has bad ContentType header.").await?;
f5ed284f8c 2025-06-21 255: },
f5ed284f8c 2025-06-21 256: };
f5ed284f8c 2025-06-21 257: };
f5ed284f8c 2025-06-21 258: };
f5ed284f8c 2025-06-21 259: let filename = if let Some(fname) = filename {
f5ed284f8c 2025-06-21 260: fname
f5ed284f8c 2025-06-21 261: } else {
f5ed284f8c 2025-06-21 262: "Attachment.txt".into()
f5ed284f8c 2025-06-21 263: };
f5ed284f8c 2025-06-21 264: files.push(Attachment {
f5ed284f8c 2025-06-21 265: data: Cursor::new(data),
f5ed284f8c 2025-06-21 266: name: filename,
f5ed284f8c 2025-06-21 267: });
f5ed284f8c 2025-06-21 268: }
f5ed284f8c 2025-06-21 269: self.tg.sendgroup(chat, files, &msg).await?;
f5ed284f8c 2025-06-21 270: } else {
f5ed284f8c 2025-06-21 271: self.tg.send(chat, &msg).await?;
f5ed284f8c 2025-06-21 272: }
f5ed284f8c 2025-06-21 273: }
f5ed284f8c 2025-06-21 274: } else {
f5ed284f8c 2025-06-21 275: bail!("Required headers were not found.");
f5ed284f8c 2025-06-21 276: }
f5ed284f8c 2025-06-21 277: Ok(())
f5ed284f8c 2025-06-21 278: }
f5ed284f8c 2025-06-21 279: }
f5ed284f8c 2025-06-21 280:
512369f93e 2026-08-01 281: /// SMTP handler implementation for mailin-embedded.
f5ed284f8c 2025-06-21 282: impl mailin_embedded::Handler for MailServer {
f5ed284f8c 2025-06-21 283: /// Just deny login auth
f5ed284f8c 2025-06-21 284: fn auth_login (&mut self, _username: &str, _password: &str) -> Response {
f5ed284f8c 2025-06-21 285: INVALID_CREDENTIALS
f5ed284f8c 2025-06-21 286: }
f5ed284f8c 2025-06-21 287:
f5ed284f8c 2025-06-21 288: /// Just deny plain auth
f5ed284f8c 2025-06-21 289: fn auth_plain (&mut self, _authorization_id: &str, _authentication_id: &str, _password: &str) -> Response {
f5ed284f8c 2025-06-21 290: INVALID_CREDENTIALS
f5ed284f8c 2025-06-21 291: }
f5ed284f8c 2025-06-21 292:
f5ed284f8c 2025-06-21 293: /// Verify whether address is deliverable
f5ed284f8c 2025-06-21 294: fn rcpt (&mut self, to: &str) -> Response {
1723b63d69 2026-08-01 295: if self.relay || self.get_id(to).is_ok() {
f5ed284f8c 2025-06-21 296: OK
f5ed284f8c 2025-06-21 297: } else {
1723b63d69 2026-08-01 298: NO_MAILBOX
f5ed284f8c 2025-06-21 299: }
f5ed284f8c 2025-06-21 300: }
f5ed284f8c 2025-06-21 301:
f5ed284f8c 2025-06-21 302: /// Save headers we need
f5ed284f8c 2025-06-21 303: fn data_start (&mut self, _domain: &str, from: &str, _is8bit: bool, to: &[String]) -> Response {
f5ed284f8c 2025-06-21 304: self.headers = Some(SomeHeaders{
f5ed284f8c 2025-06-21 305: from: from.to_string(),
f5ed284f8c 2025-06-21 306: to: to.to_vec(),
f5ed284f8c 2025-06-21 307: });
f5ed284f8c 2025-06-21 308: OK
f5ed284f8c 2025-06-21 309: }
f5ed284f8c 2025-06-21 310:
f5ed284f8c 2025-06-21 311: /// Save chunk(?) of data
a044f68fa7 2025-08-23 312: fn data (&mut self, buf: &[u8]) -> std::result::Result<(), Error> {
f5ed284f8c 2025-06-21 313: self.data.append(buf.to_vec().as_mut());
f5ed284f8c 2025-06-21 314: Ok(())
f5ed284f8c 2025-06-21 315: }
f5ed284f8c 2025-06-21 316:
f5ed284f8c 2025-06-21 317: /// Attempt to send email, return temporary error if that fails
f5ed284f8c 2025-06-21 318: fn data_end (&mut self) -> Response {
f5ed284f8c 2025-06-21 319: let mut result = OK;
14ef340959 2026-01-01 320: smol::block_on(Compat::new(async {
f5ed284f8c 2025-06-21 321: // relay mail
f5ed284f8c 2025-06-21 322: if let Err(err) = self.relay_mail().await {
f5ed284f8c 2025-06-21 323: result = INTERNAL_ERROR;
f5ed284f8c 2025-06-21 324: // in case that fails - inform default recipient
700254f838 2026-01-18 325: if let Err(err) = self.tg.debug(&format!("Sending emails failed:\n{err:}")).await {
f5ed284f8c 2025-06-21 326: // in case that also fails - write some logs and bail
f5ed284f8c 2025-06-21 327: eprintln!("{err:?}");
f5ed284f8c 2025-06-21 328: };
f5ed284f8c 2025-06-21 329: };
14ef340959 2026-01-01 330: }));
f5ed284f8c 2025-06-21 331: // clear - just in case
f5ed284f8c 2025-06-21 332: self.data = vec![];
f5ed284f8c 2025-06-21 333: self.headers = None;
f5ed284f8c 2025-06-21 334: result
f5ed284f8c 2025-06-21 335: }
f5ed284f8c 2025-06-21 336: }