Why do we need smtp

Deal with a range of different server capabilities, adjusting behaviour according to the capabilities of the receiving server. Report back to the user about error conditions or when mail is undeliverable, so that mail is not just lost.

Ideally, reside on a reliable, always-connected server with a stable IP address and a reverse DNS entry, ie an internet connection suitable for public-facing servers. This helps other systems not detect mail sent as spam. Given these requirements it makes sense to house the SMTP server on a public-facing always-on server somewhere, and to try and use a tool suited to doing that particular job. Another thing to consider is receiving returned email.

At a minimum, all outgoing email has a FROM address where a response can be sent unknown user, vacation reply, etc. In order for the return address to resolve, an MX record must exist that points to the return inbox location. Unless you are sending email from a computer with a static IP address that is always on, you are going to need a server to handle these inbound messages.

This is typically but not always handled by the same service. GMail, Outlook , and Yahoo Mail are examples of email services that are used by individuals who are sending email. For commercial email sending, there are services like MailChimp, Marketo, and Eloqua that are very good at sending mass email for a company and handling things like bounces, throttling, and deliverability.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Ask Question. Asked 5 years, 11 months ago. Active 1 month ago. Viewed 16k times. Improve this question. Tobia Tobia 2, 8 8 gold badges 33 33 silver badges 57 57 bronze badges. Add a comment. Active Oldest Votes. So mail providers do whatever they can to reduce this problem—and a large number of techniques make assumptions about the way email is delivered—the following are important considerations: Greylisting: Some providers will automatically drop a mail connection if the sender and recipient have not communicated before, and expect them to try a second time—because spammers often don't, while an SMTP server is always supposed to.

Credit for it should go to posters below as it slipped my mind, but is, nonetheless, very valid There are probably other minor concerns, but these would be the major ones. Improve this answer. Pang 1 1 gold badge 9 9 silver badges 12 12 bronze badges. Don't forget such not exactly minor things as SPF whitelisting of hosts allowed to send mail for a domain and DKIM digitally signing messages at domain level — especially the latter is only possible with a dedicated relay. If your mail client can sign the message with a published key it's as valid as any other signatory.

It is a terrific trade off. Also, some greylist systems will ommediatelly. Sadly, its very effective. Could add that in "the good ol' days" mail was often sent from one SMTP server to another, then another, then another before reaching it's destination. This usually worked fine, but for example during the rtm-worm attack, one of the computer down was one of the essential mail-relays, so emails with warning, solutions and fixes to the worm, could take as much as 48 hours to reach their recipients.

Show 2 more comments. Giacomo Giacomo Ron Maupin Ron Maupin 3, 1 1 gold badge 14 14 silver badges 23 23 bronze badges. Do you mean they won't let you make an outgoing connection to an SMTP server on port 25?

The same happens with SMTP servers—though instead of taking days, the process takes a few minutes at most. The best way to explain how SMTP works is to go over the sending process, the individual rules and commands that power it, and the errors you may encounter. Fair warning: This is where things start to get technical. Once an SMTP server is established, email clients can connect to and communicate with it. As we mentioned earlier, SMTP commands are a set of codes that power the transmission of email messages between servers.

Here are the basic SMTP commands you should be aware of:. Picture these commands as the language that allows email servers to have a conversation with each other. Their chat will look somewhat like this:. Bounces, blocks, or other issues might prevent an email from being sent. In this case, the receiving server can notify you of issues using SMTP error codes , and knowing what they mean helps you diagnose and fix email delivery roadblocks.

Check it out! The most current version is POP3 , last updated in This protocol gets its name because it operates like a real-life post office in the digital realm. POP3 will receive emails and hold them for clients until they pick them up. All emails are downloaded and stored locally, making it a handy solution for someone who only uses one computer to check emails.

In short, IMAP stores messages on an email server, but this server can be accessed by the user to check and configure their emails. What sort of advantages or disadvantages can you see from setting up and running your own SMTP server?

Now, admittedly we are going to be a bit partial here, because at Postmark we do run a super-reliable email platform that you can use to deliver email via SMTP. From signing up to social media accounts to retrieving forgotten or stolen passwords, email is a constant.

To your customers, where email is concerned, there is no room for mistakes. An SMTP relay is a guarantee When email delivery issues occur, it is common for legitimate email to end up in junk folders, or to be blocked completely. With an SMTP relay in place, you can rest assured that sent email is going where it should be going.

Spam is a constant Just as email is a constant on the internet, so too is spam. A small price to pay While nobody likes paying out money for a service, a small monthly fee pales in comparison to dealing with blacklisting and the frustrated customers and support tickets that inevitably come along with compromised email delivery.

Run by experts Running a hosting company, whether big or small, is no easy feat. Having to deal with unreliable email delivery issues is something we can take off your plate.

We have a team of specialized developers and a hour monitoring service; meaning you can rest easy in the knowledge that a team of experts is taking care of your email.