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

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  Spear Phishing , i
2 comments
Read more

Cloud Sync let you sync your Data from NAS to Cloud Storage

Cloud Sync let you sync your Data from NAS to Cloud Storage Cloud Sync  Cloud Sync integrates the advantages of public cloud and private cloud, enabling you to effortlessly connect your Synology NAS to public cloud services, such as Amazon Drive, BackBlaze B2, Dropbox, Google Cloud Storage, Microsoft Azure, OpenStack Swift, and more. Seamless synchronization between private and public clouds Cloud Sync enables you to seamlessly connect your local Synology NAS to public cloud services or on-premise storage through Amazon S3 API, OpenStack Swift, or WebDAV protocols. With Cloud Sync, you can enhance the collaboration when accessing between your local NAS and other remote cloud services, and can efficiently and easily back up data from or to public clouds. With Cloud Sync, you can seamlessly sync and share files among your Synology NAS and multiple public cloud services, including: Alibaba Cloud Object Storage Service (OSS) Amazon Drive (end of support as of November 1, 2020) Amazon S3 co
Post a Comment
Read more