How to send mass emails in Outlook (and why you shouldn’t)

Ever heard the saying cast a wide net? Great for fishing, not so great for email. In fact, sending mass email campaigns can encourage ISPs to flag you as spam, or worse. Smart sending is about deliverability. If most of your mailing list uses Outlook, sending through Outlook sounds smart. Here’s why that may not be the case.



You’ve done your market research, uploaded your contact list, and you’re ready to hit your subscribers with a mass email. If your business uses Microsoft Outlook you might wonder, “Can I just send an Outlook mass email to all my subscribers?”

While sending mass emails in Outlook is possible, there are limitations for using Outlook’s bulk email tool.

In this article, we’ll learn how to send personalized mass emails in Outlook, some wise words to remember when sending mass emails, and the benefits of using an ESP, like Sinch Mailgun, for emailing your contacts. We’ll even show you how to mass email Outlook contacts from the comfort of the Mailgun interface, and how to pull your metrics into your dashboard with Microsoft SNDS.

Why should I send mass emails?

Mass mailing is useful for reaching out to both prospective clients and longtime customers. Whether it’s a Black Friday promotion, company newsletter, or important update, the goal is the same – to land in the inbox.

Here are some examples of mass marketing emails:

  • Promotional emails inform both prospective and existing customers in your contact list about relevant products and services.

  • Email newsletters inform your subscribers of what’s happening with your brand.

  • Acquisition emails aim to convert prospective clients in your email list into actual customers.

  • Retention emails target customers who aren’t opening your emails to try to boost their loyalty by making special offers to bring them back. 

If you use them correctly, email bursts are a great way to engage with your subscriber base. They’re even more effective if you’re able to extract a bit of data and segment your emails based on your subscriber’s preferences. Practices like segmentation, or personalization helps you to avoid the spam folder and improve engagement, which really helps your deliverability.

Learn more: We’ve mentioed deliverability a few times but what does it mean? If email deliverability is a new idea that you’re wrapping your mind around, we’ve got you covered. Check out our guide to understanding email deliverability for everything you need to know.

Why shouldn’t I send mass emails in Microsoft Outlook?

Before you get started, refresh your strategy with some bulk email best practices. In addition to these tips, here are some boundaries you should keep in mind when sending mass emails with Outlook:

  • Outlook limits how many emails you can send per day.

  • Outlook limits how many recipients you can include in each message.

  • If too many of your emails are marked as spam or sent to invalid email addresses, you may encounter deliverability issues.

  • You can’t personalize emails or do everything you may want to with html because Outlook has limited design capabilities.

  • You can’t test your emails with a preview tool before sending to ensure they perform across different devices and operating systems.

Let’s dig into each of these issues below.

How many emails can I send at once in Outlook?

Before sending, be aware of Outlook's mass email limits. You can’t send more than 5,000 emails within 24 hours in Outlook. In addition, you can only send 1,000 emails to “non-relationship recipients” or users that you’ve never sent mail to before. This is clearly problematic for marketing campaigns and growing a user base.

How many recipients does Outlook allow?

Outlook doesn’t allow you to add more than 500 recipients for each email message. While the average personal email user will never hit this limit, it’s very inconvenient for businesses to have to send out multiple emails capped at 500 recipient email addresses per email.

Will I encounter deliverability issues with Outlook?

If your sender address is a Microsoft Outlook address, there’s a high chance that your email will never make it to the inbox. Outlook is an ESP designed for personal use, so most ESPs flag bulk emails from Outlook addresses as suspicious.

Learn more: If too many of your email messages are flagged as spam, it can negatively impact your deliverability. To keep your emails out of the spam folder, protect your sender and brand reputations.

What are Outlook’s design capabilities?

Microsoft Outlook doesn’t support complex design features and fails to measure up to the standards for most digital marketing campaigns. Your MS Outlook email will stand no chance against competitors armed with HTML templates, responsive designs, and interactive graphics.

Does Outlook offer a way to test my mass mailings?

Outlook doesn’t offer a way to test your emails before sending them, so you can’t validate how your messages will appear across a variety of devices. Previewing emails is an important step in sending, and it helps to be able to obtain metrics on the different devices and operating systems your recipients are using.

Why do I need an email sending service like Mailgun?

Even though Outlook has more mass mailing functionalities than Gmail, Outlook still has many limitations. We recommend using a bulk email service provider like Mailgun for your email marketing needs.

In addition to dodging all the pitfalls of Outlook mass mailings, Mailgun provides you with the tools you need to superpower your marketing automation and deliverability. We’ll increase your open rate, help retain your customers, and ensure that your mass emails land in your user’s inbox.

How is a platform like Mailgun different:

  • We check the validity of your mailing list’s email addresses with our Powerful Email API. This will help you boost your sender reputation and maintain list hygiene. Our API can also help you automate sending, testing, and logging email analytics.

  • Thanks to our Rapid Fire Throughput SLA, you won’t be rate-limited to 500 emails a day. Mailgun will ensure your time-sensitive email marketing messages are delivered quickly and without delay.

  • We can help design a deliverability strategy and provide technical expertise through our Deliverability Services to ensure your emails reach your customers’ inboxes.

  • If you’re wondering if you should update your email marketing campaign, our Email Analytics will show how your email list’s subscribers respond to your messages.

You can also bring your own responsive HTML templates and test them with our tools before blasting out your marketing campaign.

And, if you’re sure you want to send a bulk email to all of your Outlook contacts, our Mailing List API can help you export your Microsoft Outlook contacts as a CSV file. Then, you can send out a bulk email blast to your Outlook contacts through Mailgun with the added protection of additional tests and features.

How to take advantage of Microsoft metrics within your account

You may think the one disadvantage to sending through an ESP like Mailgun if all of your contacts are Outlook users, is that you loose visibility into performance. Microsoft offers it's own free postmaster service called SNDS (Smart Network Data Services) that provides senders with insight into their email program that they wouldn’t otherwise be able to see.

SNDS allows you to access data that comes directly – and exclusively – from Micorosoft mailboxes like Hotmail and Outlook. Metrics like bounces, complaint rates, and other engagement indicators can be implemented to improve your segmentation, clean your mailing list, and improve your deliverability.

Google has somehting similar with Google Postmaster Tools, and through integrations these external metrics can be brought into your Mailgun account.

Wrapping up

Sending mass emails is one of those things that is both simple yet daunting. When you understand that different mailbox providers have different protocols and standards, it makes sense to add more deliverability practices into your strategy. Not all inboxes are created equal, and neither are all senders. The deliverability strategy that’s best for you may not work for everyone.

If these Outlook insights were helpful, be sure to check out our deliverability services to find out how we can help with other mailbox insights, sender reputation, and sending practices.

Learn about our Deliverability Services

Deliverability Services

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