Best practices

Avoid email deliverability issues while sending to Microsoft mailboxes (, Hotmail, Live, MSN)

Aleksandra Duło, 21 April 2020

All mailboxes owned by Microsoft –, Hotmail, Live Mail and MSN are very popular abroad. It is estimated that they all make up 5% of the global email market. Given that about 4 billion people in the world have an e-mail account, 5% is quite a lot. How to efficiently deliver e-mails to recipient’s mailboxes who have one of Microsofts’ account?

The Microsoft algorithm issue has been raised by many of you in our recent conversations. Some of you were wondering how to contact the providers’ postmaster. All of this, especially how to build high deliverability of transactional and marketing emails by sending to Hotmail, you will learn today from our article.

How to place your email in the inbox?

Microsoft uses their own spam filters: Exchange Online Protection and SmartScreen to help protect their users from spam.

The SmartScreen filter is influenced by many factors related to the sender, including the sending IP address, domain, database quality, content and users engagement.

  • Exchange Online Protection focuses on IP and domain reputation, authentication and spammer infrastructure, and less on content filtering.
  • The SmartScreen filter is influenced by a many factors related to the sender, including i.a. the sending IP address, domain, database quality, content and users engagement.

If you’re not reading our blog regularly, you may not know how to build a high domain reputation. Here’s something to remind you: in the world of emails it is associated with a set of specific metrics. A high reputation, like a strong brand on the market, is built up gradually, and the whole process takes time. Look at the list of factors that may affect it:

However, message authentication is a way of securing email performances and proving to email providers that the message is actually sent from you and not from a spammer who pretends to send emails on your behalf. Thanks to message authentication, we protect our recipients against phishing scams and increase the delivery of our e-mails.

Microsoft supports email senders

Microsoft Smart Network Data Services (SNDS) is a program that the overseas company offers to senders to troubleshoot delivery problems. SNDS provides them with data based on current email performances to subscribers. The information includes,i.e. spam complaints or SmartScreen filter results.

Sending best practices

Below we have gathered a small summary of email sending best practices to, Hotmail, Live Mail and MSN users, including sending from new IP addresses.

Technical email aspect and providers’ limits
  • Microsoft accepts a certain maximum number of simultaneous connections to their servers. Depending on the sending reputation, it can adjust your email connection and throughput. At EmailLabs, we monitor SMTP error codes to properly fit our clients’ email performance.

Careless behavior of a sender, who – despite warnings – continues to send at a high rate, can negatively affect the reputation of his next email performances and lead to decrease in inbox placement.

If you use EmailLabs, you don’t have to worry about such technical details

Email content and design
  • Always include valid, validated URLs in your email content. Do not link to phishing sites. Make sure where the recipient will be redirected and if the website destination is valid,
  • Send messages no larger than 25 MB,
  • Do not use scripting languages, such as ActiveX or JavaScript, when designing email messages,
  • Use the standard URL format and avoid using IP addresses in links,
  • Authenticate all emails using SPF, DKIM and DMARC,
  • Avoid excessive use of Call to Action elements such as “Register today!”, “Log in now!” and “Update immediately!”. They are widely used by spammers and could contribute to deliverability problems with Microsoft mailbox users. Urgent calls to action, such as ‘Buy now’, ‘Download our app’, ‘Start saving’, ‘Get a coupon’, ‘Learn more’ is best practice, so try to test their different options to find out what works best with your recipients.
Respect your recipient’s reaction

• Make sure your brand name appears in the senders’ address so that recipients can easily identify who they received the message from

• Use the list-unsubscribe header with the mailto option

    •  if you don’t use the mailto: option, Microsoft will you’re your subscribers the option to block future messages from you,
    • using the mailto option: gives users the option to unsubscribe from receiving emails instead of blocking them in such a way that future messages from this address will be placed in the Spam folder. What’s more, remember to respond immediately to any unsubscribe requests you receive,

• Attach a visible unsubscribe link to all of your messages and immediately accept all unsubscribe requests. This should also be done using the list-unsubscribe header

Update your Junk Email Reporting Program (JMRP) account to receive complaint feedbacks. When you see subscribers who have not been engaged for a long time, try sending them an interesting reactivating email campaign. If they still do not express interest in your message, do not hesitate to remove them from your contact list

• Use the double opt-in method to attract new subscribers. Do not buy lists or collect addresses from websites and social networks

• Encourage recipients to add your sender address to the safe sender’s list. Addresses on this list bypasses the SmartScreen filter and are delivered straight to your inbox

Infrastructure warm-up

• Before you start your email sending, prepare the infrastructure in advance. Do not send high email volumes from new IP addresses;

• Gradually add new subscribers to your marketing email stream

    • New subscribers are people who have recently agreed to receive e-mails and have not received a previous marketing message from you.
    • Send a welcome email to all new subscribers. It’s best if you send this email as soon as the user opted-in. However, if you are sending a mass welcome messages to many new subscribers simultaneously, split up the send into small batches.

By sending emails from EmailLabs you do not receive unprepared infrastructure. We always make sure the dedicated IP that we provide for our clients is previously “warmed up” and recognized by the providers as trusted.

Help in solving delivery problems

Microsoft has a way of  communicating indirectly with email users, we can’t write an email to their support or make a phone call. If you notice your messages are being blocked by Microsoft servers, you can only open a support ticket in the operator’s ticket system. However, successful problem solving requests require compliance with the strict guidelines described in the form (unfortunately you cannot write much), which gives us the impression that we are treated a bit like petitioners. Indicating problems in the Microsoft system requires a lot of know-how, e.g. if you are blocked, remember to include a copy of the entire error message. Otherwise, processing your application will take much longer.

If you are a customer of EmailLabs service – we will contact with all ISPs on your behalf, including Microsoft. All you have to do is just let us know about your problem.

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