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 {
512369f93e 2026-08-01 65: /// Main asynchronous entry point for the application.
512369f93e 2026-08-01 66: ///
512369f93e 2026-08-01 67: /// Parses command-line arguments, loads configuration, and starts the SMTP
512369f93e 2026-08-01 68: /// server.
512369f93e 2026-08-01 69: ///
512369f93e 2026-08-01 70: /// # Errors
512369f93e 2026-08-01 71: /// Returns an error if configuration is invalid, files are inaccessible, or
512369f93e 2026-08-01 72: /// server fails to start.
f5ed284f8c 2025-06-21 73: pub fn new(settings: config::Config) -> Result<MailServer> {
f5ed284f8c 2025-06-21 74: let api_key = settings.get_string("api_key")
f5ed284f8c 2025-06-21 75: .context("[smtp2tg.toml] missing \"api_key\" parameter.\n")?;
f5ed284f8c 2025-06-21 76: let mut recipients = HashMap::new();
f5ed284f8c 2025-06-21 77: for (name, value) in settings.get_table("recipients")
f5ed284f8c 2025-06-21 78: .expect("[smtp2tg.toml] missing table \"recipients\".\n")
f5ed284f8c 2025-06-21 79: {
f5ed284f8c 2025-06-21 80: let value = value.into_int()
f5ed284f8c 2025-06-21 81: .context("[smtp2tg.toml] \"recipient\" table values should be integers.\n")?;
f5ed284f8c 2025-06-21 82: recipients.insert(name, value);
f5ed284f8c 2025-06-21 83: }
f5ed284f8c 2025-06-21 84:
14ef340959 2026-01-01 85: let tg = Arc::new(TelegramTransport::new(api_key, recipients, &settings)?);
f5ed284f8c 2025-06-21 86: let fields = HashSet::<String>::from_iter(settings.get_array("fields")
f5ed284f8c 2025-06-21 87: .expect("[smtp2tg.toml] \"fields\" should be an array")
f5ed284f8c 2025-06-21 88: .iter().map(|x| x.clone().into_string().expect("should be strings")));
f5ed284f8c 2025-06-21 89: let mut domains: HashSet<String> = HashSet::new();
a044f68fa7 2025-08-23 90: let extra_domains = settings.get_array("domains").stack()?;
f5ed284f8c 2025-06-21 91: for domain in extra_domains {
f5ed284f8c 2025-06-21 92: let domain = domain.to_string().to_lowercase();
f5ed284f8c 2025-06-21 93: if RE_DOMAIN.is_match(&domain) {
f5ed284f8c 2025-06-21 94: domains.insert(domain);
f5ed284f8c 2025-06-21 95: } else {
f5ed284f8c 2025-06-21 96: panic!("[smtp2tg.toml] can't check of domains in \"domains\": {domain}");
f5ed284f8c 2025-06-21 97: }
f5ed284f8c 2025-06-21 98: }
f5ed284f8c 2025-06-21 99: let domains = domains.into_iter().map(|s| escape(&s))
f5ed284f8c 2025-06-21 100: .collect::<Vec<String>>().join("|");
f748e99b70 2026-08-01 101: let address = Regex::new(&format!("^[a-z0-9][-a-z0-9]*(@({domains}))?$")).stack()?;
f5ed284f8c 2025-06-21 102: let relay = match settings.get_string("unknown")
f5ed284f8c 2025-06-21 103: .context("[smtp2tg.toml] can't get \"unknown\" policy.\n")?.as_str()
f5ed284f8c 2025-06-21 104: {
f5ed284f8c 2025-06-21 105: "relay" => true,
f5ed284f8c 2025-06-21 106: "deny" => false,
f5ed284f8c 2025-06-21 107: _ => {
f5ed284f8c 2025-06-21 108: bail!("[smtp2tg.toml] \"unknown\" should be either \"relay\" or \"deny\".\n");
f5ed284f8c 2025-06-21 109: },
f5ed284f8c 2025-06-21 110: };
f5ed284f8c 2025-06-21 111:
f5ed284f8c 2025-06-21 112: Ok(MailServer {
f5ed284f8c 2025-06-21 113: data: vec!(),
f5ed284f8c 2025-06-21 114: headers: None,
f5ed284f8c 2025-06-21 115: relay,
f5ed284f8c 2025-06-21 116: tg,
f5ed284f8c 2025-06-21 117: fields,
f5ed284f8c 2025-06-21 118: address,
f5ed284f8c 2025-06-21 119: })
f5ed284f8c 2025-06-21 120: }
f5ed284f8c 2025-06-21 121:
512369f93e 2026-08-01 122: /// Retrieves the Telegram chat ID for a given email address, checks that
512369f93e 2026-08-01 123: /// used domain is allowed.
512369f93e 2026-08-01 124: ///
512369f93e 2026-08-01 125: /// # Arguments
512369f93e 2026-08-01 126: /// * `name_str` - Email address or username to look up.
512369f93e 2026-08-01 127: ///
512369f93e 2026-08-01 128: /// # Returns
512369f93e 2026-08-01 129: /// * `Result<ChatPeerId>` - Telegram chat ID for the address, or default if
512369f93e 2026-08-01 130: /// not found.
f748e99b70 2026-08-01 131: pub fn get_id (&self, name: &str) -> Result<&ChatPeerId> {
f748e99b70 2026-08-01 132: if self.address.is_match(name) {
f748e99b70 2026-08-01 133: match self.tg.get(name) {
f748e99b70 2026-08-01 134: Ok(addr) => Ok(addr),
f748e99b70 2026-08-01 135: Err(_) => Ok(&self.tg.default),
f748e99b70 2026-08-01 136: }
f748e99b70 2026-08-01 137: } else {
f748e99b70 2026-08-01 138: bail!("Doesn't look like address from one of our domains.");
f5ed284f8c 2025-06-21 139: }
f5ed284f8c 2025-06-21 140: }
f5ed284f8c 2025-06-21 141:
f5ed284f8c 2025-06-21 142: /// Attempt to deliver one message
f5ed284f8c 2025-06-21 143: async fn relay_mail (&self) -> Result<()> {
f5ed284f8c 2025-06-21 144: if let Some(headers) = &self.headers {
f5ed284f8c 2025-06-21 145: let mail = mail_parser::MessageParser::new().parse(&self.data)
f5ed284f8c 2025-06-21 146: .context("Failed to parse mail.")?;
f5ed284f8c 2025-06-21 147:
f5ed284f8c 2025-06-21 148: // Adding all known addresses to recipient list, for anyone else adding default
f5ed284f8c 2025-06-21 149: // Also if list is empty also adding default
f5ed284f8c 2025-06-21 150: let mut rcpt: HashSet<&ChatPeerId> = HashSet::new();
f5ed284f8c 2025-06-21 151: if headers.to.is_empty() && !self.relay {
f5ed284f8c 2025-06-21 152: bail!("Relaying is disabled, and there's no destination address");
f5ed284f8c 2025-06-21 153: }
f5ed284f8c 2025-06-21 154: for item in &headers.to {
f5ed284f8c 2025-06-21 155: rcpt.insert(self.get_id(item)?);
f5ed284f8c 2025-06-21 156: };
f5ed284f8c 2025-06-21 157: if rcpt.is_empty() {
f5ed284f8c 2025-06-21 158: self.tg.debug("No recipient or envelope address.").await?;
f5ed284f8c 2025-06-21 159: rcpt.insert(&self.tg.default);
f5ed284f8c 2025-06-21 160: };
f5ed284f8c 2025-06-21 161:
0f47e23e21 2026-01-12 162: // preparing message header
0f47e23e21 2026-01-12 163: let mut reply: Vec<String> = vec!["<blockquote expandable>".into()];
14ef340959 2026-01-01 164: if self.fields.contains("subject") {
14ef340959 2026-01-01 165: if let Some(subject) = mail.subject() {
0f47e23e21 2026-01-12 166: reply.push(format!("<u><i>Subject:</i></u> <code>{}</code>", validate(subject).stack()?));
14ef340959 2026-01-01 167: } else if let Some(thread) = mail.thread_name() {
0f47e23e21 2026-01-12 168: reply.push(format!("<u><i>Thread:</i></u> <code>{}</code>", validate(thread).stack()?));
14ef340959 2026-01-01 169: }
14ef340959 2026-01-01 170: }
14ef340959 2026-01-01 171: // do we need to replace spaces here?
14ef340959 2026-01-01 172: if self.fields.contains("from") {
0f47e23e21 2026-01-12 173: reply.push(format!("<u><i>From:</i></u> <code>{}</code>", validate(&headers.from).stack()?));
0f47e23e21 2026-01-12 174: }
0f47e23e21 2026-01-12 175: if self.fields.contains("date")
0f47e23e21 2026-01-12 176: && let Some(date) = mail.date()
0f47e23e21 2026-01-12 177: {
0f47e23e21 2026-01-12 178: reply.push(format!("<u><i>Date:</i></u> <code>{date}</code>"));
0f47e23e21 2026-01-12 179: }
0f47e23e21 2026-01-12 180: reply.push("</blockquote><pre>".into());
c996f5c871 2026-01-12 181: let reply = reply.join("\n");
f5ed284f8c 2025-06-21 182:
f5ed284f8c 2025-06-21 183: let html_parts = mail.html_body_count();
f5ed284f8c 2025-06-21 184: let text_parts = mail.text_body_count();
f5ed284f8c 2025-06-21 185: let attachments = mail.attachment_count();
f5ed284f8c 2025-06-21 186: if html_parts != text_parts {
f5ed284f8c 2025-06-21 187: self.tg.debug(&format!("Hm, we have {html_parts} HTML parts and {text_parts} text parts.")).await?;
f5ed284f8c 2025-06-21 188: }
f5ed284f8c 2025-06-21 189: //let mut html_num = 0;
f5ed284f8c 2025-06-21 190: let mut text_num = 0;
f5ed284f8c 2025-06-21 191: let mut file_num = 0;
f5ed284f8c 2025-06-21 192: // let's display first html or text part as body
c996f5c871 2026-01-12 193: let mut body: String = "".into();
f5ed284f8c 2025-06-21 194: /*
f5ed284f8c 2025-06-21 195: * actually I don't wanna parse that html stuff
f5ed284f8c 2025-06-21 196: if html_parts > 0 {
a044f68fa7 2025-08-23 197: let text = mail.body_html(0).stack()?;
f5ed284f8c 2025-06-21 198: if text.len() < 4096 - header_size {
f5ed284f8c 2025-06-21 199: body = text;
f5ed284f8c 2025-06-21 200: html_num = 1;
f5ed284f8c 2025-06-21 201: }
f5ed284f8c 2025-06-21 202: };
f5ed284f8c 2025-06-21 203: */
f5ed284f8c 2025-06-21 204: if body.is_empty() && text_parts > 0 {
f5ed284f8c 2025-06-21 205: let text = mail.body_text(0)
c996f5c871 2026-01-12 206: .context("Failed to extract text from message")?
c996f5c871 2026-01-12 207: .replace("\r\n", "\n");
db04f7359b 2026-01-18 208: let text = validate(&text).stack()?;
c996f5c871 2026-01-12 209: // 6:
c996f5c871 2026-01-12 210: // - (headers)
0f47e23e21 2026-01-12 211: // - (mail text)
0f47e23e21 2026-01-12 212: // - 6: </pre>
6ce625a569 2026-01-12 213: if text.len() < 4096 - ( reply.len() + 6 ) {
db04f7359b 2026-01-18 214: body = text.to_string();
f5ed284f8c 2025-06-21 215: text_num = 1;
f5ed284f8c 2025-06-21 216: }
f5ed284f8c 2025-06-21 217: };
db04f7359b 2026-01-18 218: let msg = format!("{}{}</pre>", reply, body);
f5ed284f8c 2025-06-21 219:
f5ed284f8c 2025-06-21 220: // and let's collect all other attachment parts
f5ed284f8c 2025-06-21 221: let mut files_to_send = vec![];
f5ed284f8c 2025-06-21 222: /*
f5ed284f8c 2025-06-21 223: * let's just skip html parts for now, they just duplicate text?
f5ed284f8c 2025-06-21 224: while html_num < html_parts {
a044f68fa7 2025-08-23 225: files_to_send.push(mail.html_part(html_num).stack()?);
f5ed284f8c 2025-06-21 226: html_num += 1;
f5ed284f8c 2025-06-21 227: }
f5ed284f8c 2025-06-21 228: */
f5ed284f8c 2025-06-21 229: while text_num < text_parts {
a044f68fa7 2025-08-23 230: files_to_send.push(mail.text_part(text_num.try_into().stack()?)
f5ed284f8c 2025-06-21 231: .context("Failed to get text part from message.")?);
f5ed284f8c 2025-06-21 232: text_num += 1;
f5ed284f8c 2025-06-21 233: }
f5ed284f8c 2025-06-21 234: while file_num < attachments {
a044f68fa7 2025-08-23 235: files_to_send.push(mail.attachment(file_num.try_into().stack()?)
f5ed284f8c 2025-06-21 236: .context("Failed to get file part from message.")?);
f5ed284f8c 2025-06-21 237: file_num += 1;
f5ed284f8c 2025-06-21 238: }
f5ed284f8c 2025-06-21 239:
f5ed284f8c 2025-06-21 240: for chat in rcpt {
f5ed284f8c 2025-06-21 241: if !files_to_send.is_empty() {
f5ed284f8c 2025-06-21 242: let mut files = vec![];
f5ed284f8c 2025-06-21 243: // let mut first_one = true;
f5ed284f8c 2025-06-21 244: for chunk in &files_to_send {
f5ed284f8c 2025-06-21 245: let data: Vec<u8> = chunk.contents().to_vec();
f5ed284f8c 2025-06-21 246: let mut filename: Option<String> = None;
f5ed284f8c 2025-06-21 247: for header in chunk.headers() {
f5ed284f8c 2025-06-21 248: if header.name() == "Content-Type" {
f5ed284f8c 2025-06-21 249: match header.value() {
f5ed284f8c 2025-06-21 250: mail_parser::HeaderValue::ContentType(contenttype) => {
f5ed284f8c 2025-06-21 251: if let Some(fname) = contenttype.attribute("name") {
f5ed284f8c 2025-06-21 252: filename = Some(fname.to_owned());
f5ed284f8c 2025-06-21 253: }
f5ed284f8c 2025-06-21 254: },
f5ed284f8c 2025-06-21 255: _ => {
f5ed284f8c 2025-06-21 256: self.tg.debug("Attachment has bad ContentType header.").await?;
f5ed284f8c 2025-06-21 257: },
f5ed284f8c 2025-06-21 258: };
f5ed284f8c 2025-06-21 259: };
f5ed284f8c 2025-06-21 260: };
f5ed284f8c 2025-06-21 261: let filename = if let Some(fname) = filename {
f5ed284f8c 2025-06-21 262: fname
f5ed284f8c 2025-06-21 263: } else {
f5ed284f8c 2025-06-21 264: "Attachment.txt".into()
f5ed284f8c 2025-06-21 265: };
f5ed284f8c 2025-06-21 266: files.push(Attachment {
f5ed284f8c 2025-06-21 267: data: Cursor::new(data),
f5ed284f8c 2025-06-21 268: name: filename,
f5ed284f8c 2025-06-21 269: });
f5ed284f8c 2025-06-21 270: }
f5ed284f8c 2025-06-21 271: self.tg.sendgroup(chat, files, &msg).await?;
f5ed284f8c 2025-06-21 272: } else {
f5ed284f8c 2025-06-21 273: self.tg.send(chat, &msg).await?;
f5ed284f8c 2025-06-21 274: }
f5ed284f8c 2025-06-21 275: }
f5ed284f8c 2025-06-21 276: } else {
f5ed284f8c 2025-06-21 277: bail!("Required headers were not found.");
f5ed284f8c 2025-06-21 278: }
f5ed284f8c 2025-06-21 279: Ok(())
f5ed284f8c 2025-06-21 280: }
f5ed284f8c 2025-06-21 281: }
f5ed284f8c 2025-06-21 282:
512369f93e 2026-08-01 283: /// SMTP handler implementation for mailin-embedded.
f5ed284f8c 2025-06-21 284: impl mailin_embedded::Handler for MailServer {
f5ed284f8c 2025-06-21 285: /// Just deny login auth
f5ed284f8c 2025-06-21 286: fn auth_login (&mut self, _username: &str, _password: &str) -> Response {
f5ed284f8c 2025-06-21 287: INVALID_CREDENTIALS
f5ed284f8c 2025-06-21 288: }
f5ed284f8c 2025-06-21 289:
f5ed284f8c 2025-06-21 290: /// Just deny plain auth
f5ed284f8c 2025-06-21 291: fn auth_plain (&mut self, _authorization_id: &str, _authentication_id: &str, _password: &str) -> Response {
f5ed284f8c 2025-06-21 292: INVALID_CREDENTIALS
f5ed284f8c 2025-06-21 293: }
f5ed284f8c 2025-06-21 294:
f5ed284f8c 2025-06-21 295: /// Verify whether address is deliverable
f5ed284f8c 2025-06-21 296: fn rcpt (&mut self, to: &str) -> Response {
f5ed284f8c 2025-06-21 297: if self.relay {
f5ed284f8c 2025-06-21 298: OK
f5ed284f8c 2025-06-21 299: } else {
f5ed284f8c 2025-06-21 300: match self.get_id(to) {
f5ed284f8c 2025-06-21 301: Ok(_) => OK,
f5ed284f8c 2025-06-21 302: Err(_) => {
f5ed284f8c 2025-06-21 303: if self.relay {
f5ed284f8c 2025-06-21 304: OK
f5ed284f8c 2025-06-21 305: } else {
f5ed284f8c 2025-06-21 306: NO_MAILBOX
f5ed284f8c 2025-06-21 307: }
f5ed284f8c 2025-06-21 308: }
f5ed284f8c 2025-06-21 309: }
f5ed284f8c 2025-06-21 310: }
f5ed284f8c 2025-06-21 311: }
f5ed284f8c 2025-06-21 312:
f5ed284f8c 2025-06-21 313: /// Save headers we need
f5ed284f8c 2025-06-21 314: fn data_start (&mut self, _domain: &str, from: &str, _is8bit: bool, to: &[String]) -> Response {
f5ed284f8c 2025-06-21 315: self.headers = Some(SomeHeaders{
f5ed284f8c 2025-06-21 316: from: from.to_string(),
f5ed284f8c 2025-06-21 317: to: to.to_vec(),
f5ed284f8c 2025-06-21 318: });
f5ed284f8c 2025-06-21 319: OK
f5ed284f8c 2025-06-21 320: }
f5ed284f8c 2025-06-21 321:
f5ed284f8c 2025-06-21 322: /// Save chunk(?) of data
a044f68fa7 2025-08-23 323: fn data (&mut self, buf: &[u8]) -> std::result::Result<(), Error> {
f5ed284f8c 2025-06-21 324: self.data.append(buf.to_vec().as_mut());
f5ed284f8c 2025-06-21 325: Ok(())
f5ed284f8c 2025-06-21 326: }
f5ed284f8c 2025-06-21 327:
f5ed284f8c 2025-06-21 328: /// Attempt to send email, return temporary error if that fails
f5ed284f8c 2025-06-21 329: fn data_end (&mut self) -> Response {
f5ed284f8c 2025-06-21 330: let mut result = OK;
14ef340959 2026-01-01 331: smol::block_on(Compat::new(async {
f5ed284f8c 2025-06-21 332: // relay mail
f5ed284f8c 2025-06-21 333: if let Err(err) = self.relay_mail().await {
f5ed284f8c 2025-06-21 334: result = INTERNAL_ERROR;
f5ed284f8c 2025-06-21 335: // in case that fails - inform default recipient
700254f838 2026-01-18 336: if let Err(err) = self.tg.debug(&format!("Sending emails failed:\n{err:}")).await {
f5ed284f8c 2025-06-21 337: // in case that also fails - write some logs and bail
f5ed284f8c 2025-06-21 338: eprintln!("{err:?}");
f5ed284f8c 2025-06-21 339: };
f5ed284f8c 2025-06-21 340: };
14ef340959 2026-01-01 341: }));
f5ed284f8c 2025-06-21 342: // clear - just in case
f5ed284f8c 2025-06-21 343: self.data = vec![];
f5ed284f8c 2025-06-21 344: self.headers = None;
f5ed284f8c 2025-06-21 345: result
f5ed284f8c 2025-06-21 346: }
f5ed284f8c 2025-06-21 347: }