Skip to main content

Mail Flow Topology


It is important to understand the entire mail flow from sender to receiver. It helps to understand the entire mechanics and workings of all the several components that exists in the mail flow topology. The understanding of this will help you to troubleshoot why some email cannot be send or why you cannot receive certain emails.

A - User compose a  email using Mail Client. The email is sent from mail client to mail server via SMTP, MAPI or ActiveSync. The Mailbox maintain constant connectivity
B - Mail Server check for outgoing mail security rules/policies
C - If YES, then check for Internal Mailbox
D - Deliver to Mailboxes
E - If uncached or new MX Domain record, then query MX from DNS Server
F - Sender Mail to Receiver Mail Server via SMTP (25, 2525) or SMTPS (465) or SMTP/TLS (587)
G - Received Mail Server check SPF records
H - Mail Server check for incoming mail security rules/policies
I - Mail Server check for valid user mailbox
J - Mail Server deliver to User mailbox
K - Mail Client maintain constant connectivity between Mail Client and User Mailbox
L - Mail Client check for incoming mail security rules/policies

SMTP (Simple Mail Transfer Protocol) is a communication protocol for electronic mail transmission. As an Internet standard, SMTP was first defined in 1982 by RFC 821, and updated in 2008 by RFC 5321 to Extended SMTP additions, which is the protocol variety in widespread use today. Mail servers and other message transfer agents use SMTP to send and receive mail messages. Proprietary systems such as Microsoft Exchange and IBM Notes and webmail systems such as Outlook.com, Gmail and Yahoo! Mail may use non-standard protocols internally, but all use SMTP when sending to or receiving email from outside their own systems. SMTP servers commonly use the Transmission Control Protocol on port number 25.

SMTPS (Simple Mail Transfer Protocol Secure) is a method for securing the SMTP using transport layer security. It is intended to provide authentication of the communication partners, as well as data integrity and confidentiality.
SMTPS is not a proprietary protocol and not an extension of SMTP. It is a way to secure SMTP at the transport layer, by wrapping SMTP inside TLS. Conceptually, it is similar to how HTTPS wraps HTTP inside TLS.




Comments

Post a Comment

Popular posts from this blog

Recommended Top 3 Affordable Conference Speakerphones in 2020

In today's world, cost and affordability are more important than ever. That's why we would be keen on getting quality and lasting devices that will enhance our work-life without breaking the wallets. Now that we are in more group meetings and such, quality conferencing devices will be a key factor in delivering the best meeting experience for our clients and customers. Jabra Speak 410 (SGD $159) Fuss-free and iconic, the Jabra 410 is the most affordable speakerphone that we found and it is perfect for personal use or even a small meeting size. Simply plug and play and it is ready. Perfect when you need a personal speakerphone while working at home and simply having the flexibility to bring it to the office after Covid-19 situation is highly efficient. Yealink CP700  (SGD $169) One of the lesser-known brands in the market. Yealink actually excels in making some of the most recognisable VoIP phones in the market. Having a speakerphone section now, they are not ...
1 comment
Read more

To Phish or To Be Phished

What is Phishing? Phishing is the fraudulent attempt to obtain sensitive information such as usernames, passwords and credit card details by disguising oneself as a trustworthy entity in an electronic communication. Typically carried out by email spoofing or instant messaging, it often directs users to enter personal information at a fake website which matches the look and feel of the legitimate site. What is Spear Phishing? Spear-phishing is a targeted attempt to steal sensitive information such as account credentials or financial information from a specific victim, often for malicious reasons. This is achieved by acquiring personal details on the victim such as their friends, hometown, employer, locations they frequent, and what they have recently bought online. The attackers then disguise themselves as a trustworthy friend or entity to acquire sensitive information, typically through email or other online messaging. The main difference betwen  Phishing  and  Spea...
2 comments
Read more