Which Email Protocol Is Capable Of Sending Emails

Mail Transport Agent Configuration

Email Protocols

A Mail Transport Agent is essential for sending email. A Mail User Agent such as Evolution, Thunderbird, and Mutt, is used to read and compose email. When a user sends an email from an MUA, the message is handed off to the MTA, which sends the message through a series of MTAs until it reaches its destination.

Even if a user does not plan to send email from the system, some automated tasks or system programs might use the mail command to send email containing log messages to the root user of the local system.Fedora Rawhide provides two MTAs: Postfix and Sendmail. If both are installed, Postfix is the default MTA. Note that Sendmail is considered deprecated in MAJOROS .

Limits For Popular Email Sending Providers And Clients Like Gmail Outlook Sendgrid Etc

Email client
30 MB

ESPs size limits

You can see that most email clients are capable of retrieving 20 25 MB of email data. Its a pretty rare situation when you need to send a mass email with large attachments. But it is still possible when you send numerous booking or order confirmations, for example. However, besides general deliverability, there are few more concerns related to sending large messages. Spam score and rendering issues are the most important. Moreover, some ESPs like Postmark have additional limits for the email body size.

Wait What About Pop And Imap

POP and IMAP are two of the very first protocols developed on the consumer Internet that allowed for email clients – like Outlook, Thunderbird and others – to retrieve mail from a mail server.

The ports typically used for POP are TCP ports 110 and 995, and for IMAP are TCP ports 143 and 993, for insecure and secure sessions respectively. They were each good at doing different things, like reflecting the state of an email back to the server , or for preserving a copy of the message on a local machine for easy offline access. The latest version of POP, POP3, can be used with or without an SMTP.

This does not affect which port you can use with Mailgun. Mailgun doesnt host mailboxes, so these arent protocols we support.

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What Should You Remember About Smtp Ports

In summary, where performance is desired, Mailgun recommends utilizing our API endpoint. The amount of back and forth chatting is much less. And with our API SDKs, connecting up is pretty simple. If youre not interested in connecting via API, our SMTP endpoints are ready for your mail. Just dont forget port 587 is where the party is at as far as secure SMTPs are concerned!

To learn more, check out our Documentation for more info, or contact us and we can answer any questions you may have about SMTP ports or our email services.

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Understanding Email Message Flow From Sending To Delivery

A Guide to How E

For most users, how an email message flows from the sender to a recipients inbox is something that happens behind the scenes. When an individual or an organization sends an email, the message travels from its point of origination, such as an email client where it was composed, across the Internet to its destination. Along the way, it passes through multiple servers that help ensure it arrives at the right place. That email message flow uses a systematic process based on a number of long-established technical standards.

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In Closing: A Few Additional Details You Should Know About

Now, its worth mentioning that there exists a myriad of variations on the POP3 protocol , as well as a number of proprietary email services such as Microsofts MAPI. We havent mentioned any of those here today because they are not really necessary for an understanding of how email protocols function and how mail servers do their job.

Still, its good to be aware of them. Gotta know what your choices are, right?

Are you wondering what a private email server costs?

Ipv: Internet Protocol Version 6

IPv6 is the latest version of the Internet Protocol, a network layer protocol that possesses addressing and control information for enabling packets to be routed in the network. IPv6 was created to deal with IPv4 exhaustion. It increases the IP address size from 32 bits to 128 bits to support more levels of addressing.


  • More efficient routing and packet processing compared to IPv4.
  • Better security compared to IPv4.


  • IPv6 is not compatible with machines that run on IPv4.
  • Challenge in upgrading the devices to IPv6.

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Ftp: File Transfer Protocol

File Transfer Protocol enables file sharing between hosts, both local and remote, and runs on top of TCP. For file transfer, FTP creates two TCP connections: control and data connection. The control connection is used to transfer control information like passwords, commands to retrieve and store files, etc., and the data connection is used to transfer the actual file. Both of these connections run in parallel during the entire file transfer process.


  • Enables sharing large files and multiple directories at the same time.
  • Lets you resume file sharing if it was interrupted.
  • Lets you recover lost data, and schedule a file transfer.


  • FTP lacks security. Data, usernames, and passwords are transferred in plain text, making them vulnerable to malicious actors.
  • FTP lacks encryption capabilities, making it non-compliant with industry standards.

Choosing The Right Email Server Software

Email Protocols

If youve decided to host your own email server software, you should do your due diligence and thorough research to decide what the optimal solution for your company is. Here are some useful questions you can use to better filter your research:

  • Do I need an on-premise or a cloud-based solution?
  • How complex is it to manage this platform?
  • Is adding new users and managing/changing existing ones user-friendly?
  • Is setting up a users preferred email client a simple task?
  • Does the platform offer the webmail feature?
  • Are there any other useful features available?
  • Is email archiving included in the solution, and if it is not, can it be easily integrated?

Your end decision should be based solely on the requirements of your organization, your resources, and your IT infrastructure, and keep in mind that as long as you are well informed, there really are no bad choices.

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How Is Smtp Different From Other Email Protocols #

Cast your mind back to the definition of SMTP, and youll remember we said that it was one of many email protocols. POP and IMAP are the other two most common email protocols in use.

The main difference between these protocols is that SMTP is the only protocol for sending or pushing email from one unknown mail server to another. POP and IMAP are protocols for receiving or pulling mail for the recipient from their own mail server. So, POP and IMAP limit the transfer of mail to verified mail servers only. They cant be used for communication outside of your own networks.

Below, well give you a deeper explanation of how POP and IMAP work and how they differ from SMTP.

Boosts Your Brand Reputation

Email authentication verifies your brands domain name and email address, thereby promoting them as reputable entities. With authentication protocols like DMARC in place, your consumers wont receive phishing emails from you. As a result, they will view your brand as legit.

Since every company relies on reputation to boost sales, you need to authenticate your email to validate your online presence.

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In Short: Which Do I Use To Set Up My Email

Depending on your personal style of communicating your email provider, you can pretty quickly narrow down how you should use your email.

  • If you use check your email from a lot of devices, phones, or computers, use a webmail service or set up your email clients to use IMAP.
  • If you use mostly webmail and want your phone or iPad to sync with your webmail, use IMAP, as well.
  • If youre using one email client on one dedicated machine , you might be fine with POP3, but wed still recommend IMAP.
  • If you have a huge history of email and youre using an old mail provider without a lot of drive space, you may want to use POP3 to keep from running out of space on the remote email server.
  • If you use company email, and your company uses an Exchange server, youll have to use Exchange.

For our geekier readers who already know this stuff, feel free to join in on the discussion! Let us know how you explain to relatives and tech-challenged coworkers the difference in common email setups. Better yet, keep this guide handy and save yourself the trouble of explaining it!

Different Types Of Email

Email impersonation scams: What you or your IT staff can do

There are many types of email such are as follows:

Newsletters: It is studying by Clutch, the newsletter is the most common type of email that are routinely sent to all mailing list subscribers, either daily, weekly, or monthly. These emails often contain from the blog or website, links curated from other sources, and selected content that the company has recently published. Typically, Newsletter emails are sent on a consistent schedule, and they offer businesses the option to convey important information to their client through a single source. Newsletters might also incorporate upcoming events or new, webinars from the company, or other updates.

Lead Nurturing: Lead-nurturing emails are a series of related emails that marketers use to take users on a journey that may impact their buying behavior. These emails are typically sent over a period of several days or weeks. Lead-nurturing emails are also known as trigger campaigns, which are used for solutions in an attempt to move any prospective sale into a completed purchase and educate potential buyers on the services. These emails are not only helpful for converting emails but also drive engagement. Furthermore, lead-nurturing emails are initiated by a potential buyer taking initial action, such as clicking links on a promotional email or downloading a free sample.

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Remote Message Queue Starting

Remote Message Queue Starting enables a remote host to start processing of the mail queue on a server so it may receive messages destined to it by sending a corresponding command. The original TURN command was deemed insecure and was extended in RFC 1985 with the ETRN command which operates more securely using an authentication method based on Domain Name System information.

Smtp Vs Mail Retrieval

SMTP is a delivery protocol only. In normal use, mail is “pushed” to a destination mail server as it arrives. Mail is routed based on the destination server, not the individual user to which it is addressed. Other protocols, such as the Post Office Protocol and the Internet Message Access Protocol are specifically designed for use by individual users retrieving messages and managing mail boxes. To permit an intermittently-connected mail server to pull messages from a remote server on demand, SMTP has a feature to initiate mail queue processing on a remote server . POP and IMAP are unsuitable protocols for relaying mail by intermittently-connected machines they are designed to operate after final delivery, when information critical to the correct operation of mail relay has been removed.

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What About Port 465

Interestingly, port 465 was never published as an official SMTP transmission or submission channel by the IETF. Instead, the Internet Assigned Numbers Authority , who maintains much of the core internet infrastructure, registered port 465 for SMTPS. The purpose was to establish a port for SMTP to operate using Secure Sockets Layer . SSL is commonly used for encrypting communications over the internet.

The port was assigned for about one year when it was revoked in support of securing SMTP communications using Transport Layer Security . The nail in the coffin was a new protocol command “STARTTLS,” introduced in RFC 2487. This command allows SMTP servers to communicate over existing ports by advertising whether the destination server supports TLS encryption. If so, the sending server can upgrade the connection using the “STARTTLS” SMTP command.

Mailgun supports TLS connections, which you can verify by connecting and issuing an “ehlo” from a command line interface. The resultant “250 STARTTLS” confirms the endpoint accepts TLS connection requests.

You can test using the same command sequence on any SMTP server. Try Gmail or Yahoo, “telnet gmail-smtp-in.l.google.com 25” or “telnet mta7.am0.yahoodns.net 25”.

How Do Email Protocols Work

Email Protocols: SMTP, POP and IMAP

Lets compare email with physical mail to understand the role of email protocols.

A sender puts a letter in the post box, and then it is transferred to the local distribution center. After all security checks and sorting, the letter goes to another distribution center located in the recipients area. When the letter gets sorted again, a carrier brings it to the recipients home address.

Check out how it works in the scheme below.

An email can be sent from an email client like Thunderbird, for instance. SMTP transports that message to Gmails email server a distribution center. After that, SMTP moves it further to the recipients email server Yahoo. In the end, the message reaches the recipients inbox via POP3 or IMAP the carrier.

Note that the scheme above may be shorter since Gmail, Yahoo, Outlook, etc., are email providers and, at the same time, web-based email clients.

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Email Security: Best Practices For Business

Business owners need to bring their corporate email security up a notch from the personal protections outlined above. Failure to implement security best practices will result not only in the compromise of an individuals privacy, but the privacy of the business employees, partners and customers as well.

If youre at the head of an organization with employees, there are many company-wide measures you can take to combat phishing, malware and other cyber-threats.

Understanding Smtp Error Codes #

The email sending process doesnt always go as smoothly as in the example chatter of our email servers above. 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.

For example, here are two groups of SMTP errors that crop up often:

  • 4.X.X Persistent Transient Failure: These error codes start with the number 4 followed by two other numbers. They typically mean that theres a temporary failure with the mail server. Repeating the command again could get rid of the error, but these codes are often used by servers to keep untrusted senders at bay.
  • 5.X.X Permanent Error: These error codes begin with the number 5 and are followed by two numbers. They typically signify that the SMTP connection has dropped. If you try to resend the email, it will likely still result in the same error.

PS: if youre interested in learning more about SMTP errors, here at Postmark we started a public SMTP Field Manual to document the error codes we see most often. Check it out! You can even contribute your own entries if youve spotted an SMTP error we havent encountered before.

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