
If you are an admin for Office 365 for business subscription, contact Office 365 for business support. If you have an Office 365 for home subscription, or you purchased a one-time download of Office 2016, click the Contact Us button at the bottom of this page. This tool lets you reset recent addresses that Outlook has stored, and delete recent addresses all at once, instead of one at a time. Then Outlook opens a new email whenever you click on a mailto: link in an email or website. This tool lets you choose Outlook for Mac as your default mail application.

It also restores Outlook window size and position settings. This tool resets customization that you've made to Outlook from the Outlook menu > Preferences. For example, when search returns no results for items that do exist in your mailbox, or you get older data when you have newer items. This tool repairs search issues in Outlook for Mac. See this page for more information and learn how to install the tools: Outlook for Mac support tools. Use the following tools to resolve various Outlook for Mac issues. If this error appears when synchronizing your account, please report in Help > Contact Support. You receive Sync Error: 19803 when synchronizing your Office365 account. Please check your zoom settings if you run into this issue and adjust as appropriate. For example, if the zoom is set at 75%, the font of newly composed (or reply/forward) appears to be smaller, compared to the reading pane or an open received message (not in composing mode). This can cause a perceived smaller font if the zoom is set to less than 100%. Once the setting is applied in the Outlook profile, it will retain for all future messages until it is changed in the message Options menu. Zoom does not affect the reading pane or received messages - those will show the actual font size.

Zoom does not change the actual font size, it simply zooms in or out on the composing window text, (impacts the composing mode window of all new messages/replies). If the zoom setting is altered on a new message, the altered setting remains until changed back. The Zoom setting can be found in a new email message window by selecting the Options tab and clicking the Zoom button on the Ribbon.
