I support Microsoft Outlook and while it's a more robust Exchange client than Apple Mail, It's also missing a lot of features you get in Mail. If you visit the Microsoft forums, you'll find lots of issues with Outlook 2016.

May 18, 2019  free app, it may lose out to third-party alternatives for Mac because it doesn’t do anything further to help you rethink email. If you are looking to switch to a better email client, here are the best free and paid Apple Mail alternatives for Mac users. Related: 7 Things You Didn’t Know You Could Do with Your Email Inbox.

Regardless, you will have similar issues with Outlook. It's the number of messages in the Inbox that is the problem. She needs to archive messages to subfolders to reduce the number of messages in the Inbox.

1. Outlook for Mac works with Microsoft Exchange, Microsoft 365, Outlook.com (including Hotmail and MSN), Gmail, Yahoo Mail, and iCloud Learn more about Microsoft 365 Microsoft 365 is a cloud-based subscription service that brings together premium versions of Word, Excel, PowerPoint, Outlook and OneDrive, with the best tools for the way people.
2. When comparing Airmail vs Microsoft Outlook, the Slant community recommends Airmail for most people.In the question“What are the best e-mail clients for macOS?”Airmail is ranked 3rd while Microsoft Outlook is ranked 14th. The most important reason people chose Airmail is.
3. Outlook is our most full-featured email and calendar app, optimized for PCs and laptops. If you're a heavy email and calendar user, and you want all the advanced features and capabilities of email, such as scheduling and task management, rich formatting, or mailbox rules, Outlook is the best choice for you.
4. Nov 01, 2011  I previously utilized Entourage from Microsoft Office Mac (2008) and now Outlook for Mac(Office 2011). I have also lately begun to play with the new Lion version of Mail on my home computer. There are plusses and minuses to each product (Outlook & Apple Mail). The most obvious advantage to AppleMail is that it is free.
5. May 30, 2018  I use the Outlook for iOS app for work-related email and calendar events and the native Mail app for personal use. Both have their pros and cons, and although I could use the native Mail app for my work-related items, I like being able to switch between Mail and Calendar in the same app. Therefore, I would give the Outlook app the favorable nod.

Mac Mail App Vs Outlook Email

Exchange Basics

The Inbox syncs more frequently than any other and should be kept as clean as possible. (this is the number one cause of problems with sync). Do NOT make subfolders under the Inbox.

Any folder with more than a few thousand messages is going to take some time to fully come down when you first sync your account. Due to the design of Outlook's sync engine (and how exchange works), you will see the 512 newest messages in a folder at the initial start of sync then the rest of the folder's contents will be back filled before you see any mail that arrives after this point.

Outlook checks the server for updates every minute, any folder that has updates will subsequently be synced. Since Outlook has a limit on how many folders can be synced at a time, there can be a queue of folders waiting. The Inbox does get high priority so it will generally sync before other folders that also need to sync.

Exchange likes folders to not exceed 2GB.

Anyone having experience with the new Outlook for Mac, especially connected to an Exchange server.

How do you organize and sync your calendar and contacts with your iPhone.

Add the Exchange account to your iPhone and check sync to contacts and calendars.

Mac Mail App Outlook

Outlook only syncs to Exchange contacts and calendars. Outlook does not sync iCloud, Google or other CalDAV and CardDAV services.

Mac Mail Outlook Settings

Sync Basics

Apple Mail Vs Outlook App

CalDAV & CardDAV are protocols used by Apple, Google, Yahoo and others to sync contacts and calendars. Neither Entourage 2008 nor Outlook 2011 & 2016 support CalDAV or CardDAV.