Hotmail was the most popular and one of the first web-based email services launched in 1996. It was transformed as Outlook.com in 2013 to align with Microsoft’s desktop email application Outlook. Present, Outlook.com is one of the world’s leading mailbox providers, along with 400+ million active users.
Deliverability to Hotmail.com and Outlook.com domains concerns a lot of email marketers as Microsoft has the most dynamic filtering system, which frequently sends entirely legitimate email messages to the spam or junk folder.
To support senders understand how Outlook.com works, we will talk about Outlook’s features, whitelisting and blacklisting services, spam filtering system, and help tools.
The Inbox in Outlook.com has two tabs: Focused and Other. Email messages that users frequently interact with lands under the “focused tab,” others go to the “Other tab.”
You can determine which messages from which senders will go to the “Focused” and “Other” inbox. If you right-click the email message, you can able to select the “Always move to Focused/Other Inbox” option. Then you have to confirm your choice by clicking Yes.
The Outlook.com’s interface permits users to add an email to a category for a rapid search and view.
When you hit the “My friend’s been hacked” option, you will get a pop-up message saying, “You’re helping us fight junk by informing us about bad messages. We may share this email message with other organizations so they can help prevent unsolicited messages. Thank you.” and the email then goes to the Junk/ Spam email folder. It may be possible to tag the email address as a compromised account.
To save the most important messages, you can use the Archive option in your Outlook.com’s interface. This option allows moving an email message to the Archive folder, leaving the free space in the primary inbox.
To make your Outlook.com’s Inbox clean, you can also use the “sweep” feature to set the guidelines for email messages.
In addition to the above features, Outlook.com gives a user a majority of options to deal with incoming messages: safe mailing lists, filters and reporting, safe senders list, inbox rules, forwarding settings, reply settings, etc.
They protect their users against scam, spam, and malware, Outlook.com uses these filters as online exchange protection, Sender Reputation Data, and SmartScreen.
Exchange Online Protection (EOP) defined as a cloud-based email filtering service. Initially, an incoming message passes through connection filtering, which examines the sender’s reputation and inspects the email for malware. The majority of spam is stopped and removed by EOP at this point.
Then the email passes through policy filtering, where its evaluation procedure begins against custom transport guidelines that a user makes or enforces from a template.
Finally, the message is subject to content filtering, where content scrutinized for terminology or properties seen in spam email messages. The email determined to be spam by the content filter can be sent to a user’s junk/spam folder or the quarantine, dependent on the user’s settings.
In case the message passes all of the EOP’s filters successfully, then it’s delivered to the user’s inbox.
One more filtering system utilized by Outlook.com is SmartScreen. This system manages the hyperlinks, email content, and attachments.
In order to recognize spam, the SmartScreen filter uses machine learning from Microsoft Research, which determines from identified spam threats and user reports when email messages are labeled as “Spam” by recipients.
It permits the SmartScreen filter to differentiate legitimate and spam email messages and also determine the reputation of senders by many emails filtered as spam. The filter allows an SCL rating (Spam Confidence Level score) to each email message (the lesser the score, the better).
An email message with a score of -1, 0, or 1 is considered not spam and send to the recipient’s inbox.
An email message with a score of 5 and 6 is considered to be suspected of spam and send to the recipient’s Junk Email folder.
An email message with a score of 7, 8, or 9 is considered specific spam and send to the recipient’s Junk Email folder.
The SCL score of a message can easily found in the various x-headers of the acquired email.
Along with the Spam Confidence Level score, the Outlook.com’s filtering setup selects a Bulk Complaint Level (BCL) rating to distinguish between bad and good senders.
A rating 0 shows that the message is not from a bulk sender and can deliver to the inbox.
A rating 1, 2, 3 shows that the email message is from a bulk sender that generates few complaints and might be delivered to the inbox.
A rating 4, 5, 6, 7 means that the message is from a bulk sender that originates a mixed number of complaints. The email can still be delivered to the inbox.
A rating 8, 9 means that the message is from a bulk sender that originates a vast number of complaints. The message will be sent to the Junk folder.
The BCL rating exposes in the X-Microsoft-Antispam header of every message received by Outlook.com.
Outlook.com relies heavily on its Sender Reputation Data (SRD) network when filtering inbound email.
The SRD program is known as the Microsoft Spam Fighters program. It helps receive a better image of a sender’s reputation by utilizing feedback from trusted voters and enhance the filtering system that classifies emails as spam and good based on content and sender reputation.
Active Outlook.com users from more than 200 countries are casually selected as participants of the SRD program.
To get consumer feedback, Microsoft resends copies of email messages that SRD participants received in the previous 24 hours. The email comes from Microsoft Spam Fighters and requests the user to vote whether the email is junk or not junk.
SRD feedback provides a good picture of the sender’s reputation than complaints’ reports because while senders can decrease their complaint rate by sending a significant volume of emails, they cannot artificially reduce SRD junk rates.
Outlook.com doesn’t take a user’s engagement into account (except Sender Reputation Data and spam complaints) when filtering emails as Gmail does it. However, similar to Gmail, Outlook.com checks the email infrastructure utilizing the following characteristics: sender reputation and email authentication.
Like other mailbox providers, Outlook.com needs senders to authenticate their messages accurately by using these authentication methods:
Whether or not the email passed the SPF, DKIM, and DMARC authentication check is revealed in the email header Authentication-Results field.
With email authentication, sender reputation is an essential factor that determines whether the message will go to the inbox or junk. The sender’s reputation is calculated according to the sent volume, complaint rate, and spam trap hits.
In order to know your sending metrics with Outlook.com, We recommended that you sign-up with the Outlook.com Smart Network Data Services.
The SNDS report gives an overview of your IP addresses and reveals relevant statistics like complaint rate, approximate inbox rate, and trap hits.
To categorize the sender reputation, Outlook.com uses a color system which specifies an Inbox potential:
Outlook.com does not manage a proprietary whitelist where senders could submit their domains and IPs to be considered trusted senders.
But Outlook.com contributes to ReturnPath’s Certification Program that gives preferential treatment to accredited senders, permit them to bypass certain filters and land in the inbox.
Outlook.com does not have a world blacklist. But each Outlook.com consumer can make their own blocked senders’ list in their account.