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Office 365 SMTP, IMAP & POP Server Settings (Explained). Firstly, a mail server is a program that takes incoming email from local users and remote senders and routes outgoing messages for delivery.

To use Office 365 to receive or send these emails, you need to synchronize it with Microsoft Outlook. To do this, you need to use the appropriate SMTP, POP, or IMAP settings for Office 365 to facilitate this.


Microsoft Office 365 Exchange Online supports both SMTP, POP3 and IMAP protocols for clients to send and receive email messages.
So what’s the difference between SMTP, POP and IMAP?

SMTP Explained

SMTP (Simple Mail Transmission Protocol) is an email application layer protocol. To send email via SMTP, a client initiates a TCP connection to an SMTP server, which always listens to the appropriate port, which is TCP 25 by default. However, this may also be port 587 and 465. It is important to note that in order to send emails from Office 365, SMTP settings must first be configured in the email client.

Office 365 SMTP FAQs

Is SMTP Relay Supported in Office 365?

Yes, Microsoft 365/Office 365 is used as an SMTP relay.   Additionally the Office 365 SMTP relay allows you to create connectors for sending emails.

How can I configure Office 365 as an SMTP?

SMTP authentication is disabled in Microsoft 365 by default (SMTP AUTH). However, it may be activated on the Microsoft 365 control panel.  

What is POP?

Simply put, POP3 (Post Office Protocol 3) is an email receiving protocol. POP3 was basically designed to erase email messages from a mail server after they had been downloaded by an email client. It is important to note that this functionality also applies to Exchange Online servers. Therefore Office 365 Outlook’s web interface cannot display POP3-downloaded emails.

The following procedure is used to retrieve email with a POP client:

  1. First, it connects to the email server through ports 110 and 995 for SSL/TLS communications.
  2. It retrieves your email messages.
  3. Then it erases all backups of emails from the server.
  4. Finally, it breaks off connection with the server

The server can be set up to maintain a duplicate of the messages downloaded by POP clients notwithstanding POP3’s routine erasure of received emails.

Ideally using POP3 to receive email on email clients may not be practical if you need to access your mail from a variety of devices.

IMAP Protocol

Besides POP3, IMAP (Internet Message Access Protocol) is also an alternative protocol for receiving emails. In contrast to POP3, when using IMAP, email messages are saved on a mail server and are not erased when a user receives email.

The following describes the operation of an IMAP email server:

  1. First, it establishes a connection to the mail server on port 143; SSL/TLS connections use port 993.
  2. Then it searches and retrieves emails
  3. Finally it disconnects after closing the email client app.

With a local email client, a user organizes and synchronizes received email messages into folders. IMAP may be preferable, if you need to use email clients on both your home and business computers or if you use both a web interface and an email client.

Advantages of IMAP over POP



There is just one way communication: Emails are retrieved from the server without any further synchronization between the server and the client.  There is no way to track which emails have been read and which have not.  

There is 2-way communication: Emails are synchronized in both directions, from the server to the various clients, all the time. In IMAP emails retain their read/unread state even after being deleted. Additionally, all devices immediately reflect whatever changes you make to the emails. 

Only be accessed from a single device.

Access your emails from multiple devices.

Unless the option to “Keep a copy on the server” is provided, downloaded emails are permanently erased from the server.

Stored indefinitely on the server and can be retrieved at any time.

Emails are downloaded to the smartphone, using up space on the device’s local storage.

IMAP has better storage utilization. It stores emails on a remote server, it frees up space on your local device.

Unless you manually backup your emails, emails are not backed up.

Emails are backed up automatically for future retrieval.

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How to locate your Microsoft 365 Server settings

It is recommended configuring your Microsoft 365 account to use Exchange settings. Nevertheless, it’s true that not all email clients are compatible with Exchange, and therefore you may have to manually configure your server settings instead. Please follow the following steps to do so.

  1. Log in to Outlook online by entering your Microsoft 365 email address and password.
  2. To see all of Outlook’s configuration options, click the gear icon in the top right corner.
  3. To sync your inbox, click on Mail and then Sync Mail. Microsoft 365’s POP, IMAP, and SMTP server information is displayed here.
  4. Then click on settings, and then mail flow.
  5. Finally use your incoming mail port (IMAP or POP) and outgoing mail port (SMTP) to configure your email client oiMGEr device.

Office365 SMTP Configuration Cettings

Server for SMTP: smtp.office365.com

Port: 587 

Is TLS necessary? Yes, it is if it’s available.

Is SSL necessary? Yes

Authentication: Yes (select Login if multiple options are available)

Username: Your username should be your Microsoft 365 email address in its entirety. 

Password: Password should be Your Microsoft 365 password -the same as your email password.

Sometimes you might encounter some issues when configuring these SMTP settings. To resolve this, ensure that SMTP authentication is enabled in your Microsoft 365 admin.

Office 365 IMAP Settings

All in all, IMAP’s ability to allow two-way syncing makes it the preferred choice when you need to receive emails from multiple devices. To configure your Office 365 IMAP settings, you need to key in the following configuration settings:

IMAP Server: outlook.office365.com

Port: 993

Method of encryption: TLS

Username: Full Microsoft 365 email address.

Password: Should be the password associated with your Microsoft 365 email address.

Office365 POP3 Settings

It’s not often advisable to use POP3 for receiving emails due to its limitations, as mentioned above. However, POP3 is good, if you only have a single device. Please configure the following Office365 settings to use it:

Server: outlook.office365.com

Method of Encryption: TLS

Port: 995

Username: Full Microsoft 365 email address.

Password Input: Associated with your Microsoft 365 email address.

Common Configuration Errors

Error 1:

Authentication failed

Most likely because Microsoft has disabled basic authentication for your account.

A recommended solution to this is that instead of logging in using a username and password, you should utilize OAuth authentication. Before doing this, verify that your username and OAuth provider are correct if you have already set up OAuth.

Error 2:

Password error: Logon failure: unknown user name or bad password

Either your Office 365 login credentials are incorrect or Office 365 does not recognize your username.

Recheck your username and password, and please note that the passwords are case-sensitive.

Please note that sometimes, in addition to a username and password, you may need to use OAuth to access your account.

Error 3:

Connection timed out or Could not connect to…

These errors indicate that a necessary port on your server’s firewall is being blocked.

Make sure that TCP ports (587, 995, and/or 993) are open by getting in touch with your hosting business and requesting that they unblock these ports.

Error 4:

Office365 SMTP Error: 554 5.2.0 STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied

Verify that the “From” email is set to the SMTP email address (Hesk settings > General tab) and that an email address is NOT entered in the “From” name field.

Office 365 SMTP, IMAP & POP Server Settings (Explained) Conclusion

This article equips you with the appropriate knowledge for configuring your mail server settings with Office 365.

However, it is important to note that before configuring an email client, custom app, or scanner to access Office 365, you should check whether or not your company mandates MFA.

If multi-factor authentication is required, consult with an Office 365 admin to determine the best solution for connecting to Office 365 mail services.


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Josiah Mutuma

Josiah Mutuma

Josiah is a tech security expert and has been a writer for over 5 years. Follow this blog to learn more on Microsoft and Cyber security.

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