Business account, can't send a bullk email to customers

Dear @Heather Day,

Thank you for posting your question in the Microsoft Q&A forum. The issue you are encountering is a known limitation and a common point of confusion in the New Outlook for Windows, specifically when using an IMAP account. 

The core of the problem is that contact lists (also known as "contact groups") created with an IMAP account are saved locally to your computer. The New Outlook's sending function often fails to correctly "expand" these local list names into individual email addresses, which is why it highlights the list name in red and gives the "Couldn't send this message" error. 

Here are the most effective solutions to get your emails sent reliably. 

Solution 1: Use Mail Merge 

This is the most professional and reliable method for sending bulk emails to a contact list. It sends a separate email to each recipient, which helps avoid being flagged as spam and allows for personalization. 

1. Open Microsoft Word. 
2. Go to the Mailings tab and click Start Mail Merge > E-mail Messages. 
3. Click Select Recipients > Use an Existing List, then choose New Source to open the Data Connection Wizard. 
4. Choose the type of data source you want to use for the mail merge, and then select Next. 

1. Follow the prompts in the Data Connection Wizard to complete the data connection to the merge document. 

1. After setup is complete, choose File > Save. 
2. Choose File > Save. 
3. Write your email message in the Word document. You can even add personalized fields like a name. 
4. When you are finished, click Finish & Merge > Send Email Messages. 

1. In the pop-up box, ensure the "To:" field is set to the email address field, enter your subject line, and click OK. 

Outlook will then send the emails one by one. 

Official Guide: For a detailed walkthrough, please see the official Microsoft documentation: Use mail merge to send bulk email messages 

Solution 2: Manually Expand the Contact List (Quick Workaround) 

If you need to send an email immediately and don't want to use Mail Merge, you can try to manually force the list to expand before sending. 

1. Create a new email in Outlook. 
2. Do not type the list name in the "To:" field. Leave it blank for now. 
3. Go to the People section (your contacts) in Outlook. 
4. Find and double-click the contact list you want to use (Or if no contact list is available, you can create it from scratch)  

1. At the top of the list members, there should be an option to Expand the list. Sometimes this appears as a small "+" icon next to the list name. Clicking this should replace the list name with all the individual email addresses. 

1. Once expanded, you can copy all the addresses and paste them into the "Bcc:" field of your new email. (Using Bcc is best practice to protect your customers' privacy). 

Important Note: This workaround may fail if your email provider has a limit on the number of recipients per email. 

Official Guide: For a detailed walkthrough, please see the official Microsoft documentation: Manage your contacts and Contacts list - Microsoft Support 

A Note on Sending Limits 

Please be aware that most email providers, including those accessed via IMAP, have daily or hourly sending limits to prevent spam. If you are sending to a very large list, it is best to break it up into smaller batches or use a dedicated email marketing service. 

Please let me know if you have any more questions. 

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".   

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.