Understanding Inbound SMTP Relay And Crucial Points To Consider Before Configuring Inbound SMTP Relay Functions
SMTP, or Simple Mail Transfer Protocol, is a general protocol that controls the transmission and distribution of emails. As a part of the TCP/IP protocol that deals with the application, it uses the ‘store and forward’ process to direct an email over the internet. Both outbound SMTP and inbound SMTP relays serve as nodes for such transmission of emails broken down into data discernible by the servers. It is essential to understand how SMTP servers work.
Understanding How SMTP Server Works With Simple SMTP Examples
An SMTP server is a sophisticated tool that controls the transmission of emails from one location to another but also provides many additional features for security and efficiency. A professional SMTP for sale costs relatively more than the regular SMTP servers, which are usually available for a low cost or even for free. However, a regular one is usually not recommended, as unlike a professional SMTP server, it does not use a controlled IP but rather uses a non-dedicated IP, which can be easily spammed. It also has a stringent limit to the number of outbound and inbound SMTP relays, which makes it difficult to relay bulk emails.
SMTP server price varies with additional features and the number of relays that it provides. It is crucial to pick the right SMTP server to avoid any of the problems mentioned above.
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What Is Inbound SMTP Relay?
Transferring an email from one server to another, as a part of the email delivery process, is called a relay. In simple words, relaying is simply one server receiving an email from another. It is known as a relay because it is not the final destination but rather functions as a point to receive emails and distribute them to their proper locations.
SMTP relay routes email through servers to deliver and receive bulk emails. Outbound and inbound SMTP relays refer to specific relays dedicated for routing emails between SMTP servers. The function of an inbound SMTP relay is to filter the emails being received by the user’s primary server by identifying spam emails, any emails that consist of the wrong destination domain address, and emails with URLs or attachments containing threats like viruses or malware.
A properly configured inbound SMTP relay serves as a firewall against all threats to the user’s exchange server as it only allows trusted SMTP servers to communicate with the exchange server. It is important to note that the inbound SMTP relay can only accept email from the user-hosted domains. In other words, it will reject any emails from an unauthenticated domain not hosted by the user. It prevents external SMTP servers and clients from spamming through the user’s SMTP server. Being able to reject any mails received by such unauthorized domains is thus an essential characteristic of an efficient inbound SMTP relay.
The SMTP service on the relay device has to be configured to execute inbound SMTP relay functions while keeping the following key requirements in mind
- The inbound SMTP relay accepts emails from only the domains hosted by the user and otherwise authorized domains. In contrast, an outbound SMTP relay functions on all domains as the user may send email to any random domain.
- The SMTP relay must not be an open relay as it makes it vulnerable to spammers and malware threats.
- The SMTP relay machine can authenticate remote senders not using the domain hosted by the user so that they can send emails using the inbound SMTP relay.
There are emails by spammers and malicious actors that a user does not want in their inbox. At the same time, many emails are important and should be received on time, like transactions and deadline notifications. Users can control their email transmissions by efficiently configuring their relay machines for the inbound SMTP relays. Thus, inbound SMTP relays help one to efficiently manage one’s inbound email communication and keep away malicious and unwanted emails.
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