Luckily, there are several alternative, more modern ports you can use freely instead. When sending emails this way, you may often hit an error that would indicate that port 25 is closed for email submission. It’s not recommended to use for email submission unless you specifically manage your own mail server. These days, port 25 is mainly used for SMTP Relaying – transmitting messages between different email servers. This, as a result, led to more and more hosting providers and ISPs blocking port 25 for email submission. Spammers were roaming freely, sending huge waves of spam over this somewhat ancient port. Over time, though, 25 became a port for sending not only legitimate messages but also unwanted emails. It remained omnipresent for all these years and even now is used for many transmissions. When RFC 821 was launched back in 1982, it established Port 25 as the default transmission channel for internet email. As a matter of fact, it was around since the very first days of email transmission. Port 25 is the oldest of all SMTP protocols. SMTP Ports – different ports for different purposes Port 25 To understand why, we need to look a bit back into history. Other ports can also be used for SMTP transmission but they’re not usually the first choice for Internet Service Providers (ISPs).Īmong these four, 5 are the more reliable options these days. There are four of them that are or were considered standard at some point. We’ve covered SMTP Relay in detail in another article. Frequently, different ports are used for each of these stages. SMTP Relay refers to the process of relaying a message between email servers (known as MTA), on the way to the recipient’s server. Submission is, well, about submitting an email message to an outgoing server. Modern SMTP transmission can be broken down into two stages – email submission and relaying. Each email is sent to a dedicated server and a predefined SMTP port. When sending emails, SMTP first needs to direct them to a specific address on the internet for further processing. For example, to open an HTTP address you use port 80 and to get to an HTTPS address you need to use port 443. They’re a part of every domain address, even though they’re not visible to end-users. Ports (not in a maritime sense) are communication endpoints commonly used to identify the exact location of an internet address. From there, it’s usually delivered to their client over a different protocol – usually IMAP or POP3. It’s what moves the message from your email client through email servers to the recipient’s server. SMTP (Simple Mail Transfer Protocol) is a technology that sends the huge majority of emails on the internet. Let’s start with some definitions so it’s clear what we’re talking about. SMTP and SMTP ports – what are they all about? This is when knowing what the alternatives are might really help. Sometimes, however, the default SMTP port might not guarantee the best delivery. And they care about the successful delivery as much as you do. Luckily, it’s not something you need to think about a lot as your email provider does it for you. Picking the right port for an email transmission can make the difference between your email being delivered or not.
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