Friday, November 8, 2013

Dovecot MTA

I've never really wanted to create my own MTA, because I like Postfix quite a lot. And I always thought it would require a horribly lot of time to be able to create something that was anywhere even close to having Postfix's features. (I would shudder to even think about recreating Dovecot from scratch nowadays.) But slowly over time I've also been thinking of ways how things could be done a bit better, and I think I have enough ideas to start thinking about Dovecot MTA more seriously in a few more months (after my current busy schedule calms down a bit). And (unlike Dovecot!) I'm not planning on taking over the world with the MTA (or at least not very quickly), but it would definitely be useful for many installations I know of.

My main design goals for the MTA are:
  • In normal load don't queue mails, just continue delivering the mail through different processes/services until it succeeds or fails, and only after that return ok/failure to the SMTP client. So there's no (forced) post-queue filtering, everything would normally happen pre-queue. This is required because in Germany (and EU in general?) you aren't allowed to just drop spams after SMTP server has responsed OK to the client, even if you’re 100% sure it’s a spam. So this would also mean that the SMTP DATA replies will come more slowly, which means that the SMTP server must be able to handle a lot more concurrent SMTP connections, which means that in large installations the smtpd process must be able to asynchronously handle multiple SMTP client connections.
  • In some cases you can't really avoid placing mails into a queue. This could be because of temporary failures or maybe because of an abnormal load spike. A mail queue in local disk isn't very nice though, because if the local disk dies, the queued mails are lost. Dovecot MTA will allow the queue to be in object storage and it will also likely support replication (similar to current dsync replication). In both of these cases if a server dies, another server can quickly take over its queue and continue handling it.
  • Dovecot MTA is a new product, which means we can add some requirements to how it's being used, especially related to securely sending emails between servers. It could do a bunch of checks at startup and fail to even start if everything isn't correct. Here are some things I had in mind - not sure if all of these are good ideas or not:
    • Require DKIM configuration. All outgoing mails will be DKIM signed.
    • Require the domain’s DNS to contain _submission._tcp SRV record (and actually might as well require _imap._tcp too)
    • Require SSL certificates to be configured and always allow remote to use STARTTLS
    • Require DANE TLSA record to exist and match the server's configured SSL cert
    • Have very good (and strict?) DNSSEC support. If we know a remote server is supposed to have valid DNSSEC entries, but doesn't, fail to deliver mail entirely?
    • Add a new DNS record that advertises this is a Dovecot MTA (or compatible). If such entry is found (especially when correctness is guaranteed by DNSSEC), the email sender can assume that certain features exist and work correctly. If they don't, it could indicate an attack and the mail sending should be retried later. This DNS record would of course be good to try to standardize.
  • Configuration: It would take years to implement all of the settings that Postfix has, but I think it's not going to be necessary. In fact I think the number of new settings to dovecot.conf that Dovecot MTA requires would be very minimal. Instead nearly all of the configuration could be done using Sieve scripts. We'd need to implement some new MTA-specific Sieve extensions and a few core features/configurations/databases that the scripts can use, but after that there wouldn't be really any limits to what could be done with them.
  • Try to implement as many existing interfaces as possible (e.g. Milter and various Postfix APIs like policy servers) so that it wouldn’t be necessary to reimplement all the tools and filters.
So perhaps something like this could be done in time for Dovecot v2.4. Any thoughts/ideas/suggestions?

51 comments:

  1. You have touched some pleasant factors here. Any way keep up writing. 바카라사이트

    ReplyDelete
  2. Nice one! thank you so much! Thank you for sharing this post. Your blog posts are more interesting and impressive. 바카라사이트

    ReplyDelete
  3. Good post. I study one thing more difficult on totally different blogs everyday. It can all the time be stimulating to learn content from different writers and follow a bit one thing from their store.
    majortotosite
    racesite
    oncasinosite
    totopick

    ReplyDelete
  4. I would appreciate you that you pick up an important topic to write a thoroughly informative post on. I hope that you never stop and keep posting such valuable content 바카라사이트

    ReplyDelete
  5. MEGA GAME, try all slots for free credit. mega game

    The best online slots game PG SLOT direct website. https://pgslot-games.com/


    The best online slots game PG SLOT direct website. https://pgslot-games.co/

    ReplyDelete
  6. I would like to use the ability of saying thanks to you for this article here. I have usually enjoyed checking out this site. 온라인카지노

    ReplyDelete
  7. betflix Slots Auto Deposit-Withdrawal Financial System Safe, Accurate, Fast

    ReplyDelete
  8. I don't usually comment, but I have to say thank you for this amazing post.

    토토
    안전놀이터
    우리카지노탑
    카지노사이트

    ReplyDelete
  9. Thanks For sharing such valuable information. 토토사이트

    ReplyDelete

  10. Thanks again for the post. Great blog. Cool.
    I like the helpful information you provide in your articles.
    스포츠토토365

    ReplyDelete
  11. I do agree with all of the ideas you’ve presented in your post.바카라사이트닷컴

    ReplyDelete
  12. vape modules from famous brands, they're all here.Long-term stable supply, holiday discounts, regular discount code issued.Augvape KitsArtery Nugget GT.
    vapeciga

    ReplyDelete
  13. 토토사이트
    Really a great addition. I have read this marvelous post.

    ReplyDelete
  14. Thanks for Nice and Informative Post. This article is really contains lot more information nice web info for you 토토사이트

    ReplyDelete
  15. The evolution of the peppered moth is an example of natural .토토사이트

    ReplyDelete
  16. I have read several articles on your webpage that have characteristics that I want to learn about, which is why I keep coming back. As a student who frequently uses assignment help edinburgh service and requires help with his assignments, I am thrilled to learn about those blogs.

    ReplyDelete
  17. thank you for sharing this post! you done great effort
    Abogado DUI Fredericksburg

    ReplyDelete
  18. This is to helpful, I have read here all post.

    ReplyDelete
  19. Nice informative blog to read. Thanks for sharing this beautiful post. Keep sharing more interesting and informative blogs like this. Reckless Driving Rockbridge VA Lawyer

    ReplyDelete
  20. Replies
    1. yargıtay'a göre kira artış oranları
      tefe tüfe hesaplama. tablosu

      kira artış hesaplama 5. yıl sonunda kira artışı nasıl hesaplanır

      İşyeri kira ARTIŞ oranı
      Asılsız iftira cezası nedir?

      Delete
  21. This article is an appealing wealth of useful informative that is interesting and well-written. I commend your hard work on this and thank you for this information.Frederick Traffic Lawyer

    ReplyDelete
  22. "What a fantastic blog post! Your words exude positivity and inspire readers to embrace optimism. I love how you highlight the beauty in everyday moments, reminding us to cherish life's small joys. Thank you for sharing your uplifting perspectivey!Monmouth County Trespassing Lawyer

    ReplyDelete
  23. "Dovecot IMAP Server Development is an exceptional resource for those seeking to deepen their understanding of IMAP server technology. The book provides comprehensive insights into Dovecot's architecture, configuration, and customization, offering practical examples and best practices. It's an invaluable guide for both novice and experienced developers looking to enhance their IMAP server skills."Lunenburg DUI Lawyer Virginia

    ReplyDelete
  24. In the realm of healthcare, communication is key. Nurse-Led Health Webinars serve as a bridge between healthcare providers and the public, eliminating barriers of time and location. These webinars offer a NURS FPX 6011 Assessment 3 Evidence-Based Population Health Improvement Plan EN platform for nurses to convey medical concepts in accessible language, demystify complex topics, and address common misconceptions.

    ReplyDelete
  25. motorcycle accident maryland
    Dovecot MTA is a reliable and secure mail transfer agent with a strong track record in the email server landscape. Its focus on scalability and performance optimization makes it versatile for various server setups. The positive review highlights Dovecot's commitment to providing a stable and efficient email delivery solution. Overall, Dovecot MTA is a solid choice for those seeking a dependable mail transfer agent with a strong track record.

    ReplyDelete
  26. Abogado De Trafico En Virginia
    Dovecot MTA is a reliable mail transfer agent known for its exceptional performance and security features. Its flexibility and ease of integration make it a preferred choice for many. The comprehensive and user-friendly documentation makes it accessible for beginners and experienced system administrators. The MTA's focus on security ensures private and secure email communications. As a reliable, feature-rich solution, Dovecot MTA stands tall in the world of email servers, making it a trustworthy choice for anyone in need of a powerful MTA.

    ReplyDelete
  27. In the ever-evolving field of healthcare, nursing professionals play a vital role in delivering quality patient care. Alongside their clinical duties, nursing students often face the daunting task of completing various NRS 493 Benchmark Capstone Change Project Objectives assignments and projects. These assignments not only contribute to their academic grades but also enhance their understanding of crucial nursing concepts. In this digital age, online assistance from nursing experts has emerged as a valuable resource for students striving to excel in their studies. This article delves into the importance of expert online assistance for navigating nursing assignments, outlining its benefits and offering guidance on how to make the most of this resource.

    ReplyDelete
  28. In the dynamic realm of healthcare, nursing students shoulder the dual responsibilities of mastering intricate medical concepts and delivering compassionate patient care. Amidst this demanding NURS FPX 4020 Assessment 1 Locating Credible Databases and Research journey, the weight of nursing assignments often becomes a significant challenge. Enter virtual nursing assignment support, an invaluable lifeline that offers expert guidance and assistance in navigating the complex landscape of academic tasks. This article delves into the pivotal role of virtual nursing assignment support, highlighting its benefits and providing insights into optimizing its use for academic success.

    ReplyDelete
  29. Traffic Lawyer Suffolk VA
    Dovecot is an email server and IMAP/POP3 server software that is not an MTA (Mail Transfer Agent). It is easy to install and has clear documentation, but may require some configuration expertise for complex environments. Dovecot is known for its excellent performance and scalability, suitable for small and enterprise-level email deployments. It offers security features like SSL/TLS support and authentication mechanisms, and regular updates are crucial for maintaining security. The Dovecot community is active and helpful, and the official documentation is comprehensive. Dovecot supports various email protocols, including IMAP and POP3, and integrates well with other email-related software like Postfix for mail delivery. To ensure the latest security patches and improvements, users should keep Dovecot updated. Overall, Dovecot is a robust choice for those looking to set up a secure and reliable email server.

    ReplyDelete
  30. This comment has been removed by the author.

    ReplyDelete
  31. This comment has been removed by the author.

    ReplyDelete
  32. Dovecot is an open-source mail transfer agent (MTA) written in C. It is designed to be secure, efficient, and easy to use. Dovecot is used by many large organizations, including Google, Facebook, and Red Hat.Dovecot MTA is a good choice for organizations that are looking for a secure, efficient, and easy-to-use MTA.
    lawyer for flsa claim
    arbitration for contract disputes

    ReplyDelete
  33. Don't stop writing! Your blog is becoming one of my favorites, and I look forward to your future posts.Nota de Emisión Divorcio Nueva York

    ReplyDelete
  34. This comment has been removed by the author.

    ReplyDelete
  35. This comment has been removed by the author.

    ReplyDelete
  36. Estate Lawyer Near Me
    Dovecot MTA is a robust and reliable email server solution that offers compatibility with various email protocols like IMAP and POP3. Its modular architecture allows for easy customization and scalability, and its comprehensive documentation is user-friendly. The software supports multi-tenancy, monitoring, logging, and regular updates. Its plugin system allows users to extend functionality based on their specific needs. The software's resource-efficient design ensures minimal hardware requirements, and it supports server-side email filtering and scripting. However, it could benefit from more user-friendly graphical interfaces, real-world examples, and more advanced email features like PGP encryption. Regular security audits and vulnerability assessments would enhance trust. A user-friendly GUI-based administration tool would make it more accessible to newcomers. The software's open-source nature allows for transparency and trust.

    ReplyDelete
  37. Timo Sirainen's article on Dovecot MTA and clustering with dsync-based replication offers a detailed exploration of potential improvements and features in email servers. The author addresses real-world issues, such as spam handling, SMTP connections, and high availability. The article provides technical details, diagrams, and explanations, making it a valuable resource for email server technology enthusiasts. wills and estate lawyer near me

    ReplyDelete