What's not supported in Outlook Mail
Here are a few features that G Suite Sync for Microsoft® Outlook® (GSSMO) does not support in Outlook Mail. These features either aren't available in Outlook, or they might not work as you'd expect.
The following features are not supported
Recovering deleted items
After emptying your Deleted items folder, you can't use "Recover Deleted Items" in Outlook's Tools menu to get the messages back. (This menu item isn't available.)
Sharing mailbox folders
You can't share a mailbox folder in Outlook with other users (Permissions settings aren't available in the folder's Properties dialog). This is because folders in Outlook map to labels in Gmail, which don't have permission properties.
Public folders aren't available with GSSMO (they're missing from Outlook's navigation pane).
Sending executable attachments or .eml and .msg attachments from Outlook
GSSMO doesn't allow sending executable file attachments (including executables in compressed attachments) from either Outlook or the Gmail interface. There also limitations when you send .eml or .msg attachments to Microsoft® Outlook users. See Can't view MSG or EML files.Which file types can I not send?
.hta, .ins, .isp, .jse, .lib, .mde, .msc, .msg, .msp,
.mst, .pif, .scr, .sct, .shb, .sys, .vb, .vbe,
.vbs, .vxd, .wsc, .wsf, .wsh
Delivery receipts aren't generated in Outlook when using GSSMO. If you request a delivery receipt for a message you send from Outlook, you won't receive a response when the message is delivered. However, you can select a read receipt (see below).
The features below are available but may not work as you expect
Read receipts are generated in Outlook with GSSMO. However, your recipient must be using Outlook and must enable read receipts for their profile. In that case, you'll get a response when your message is read.
Out of Office (OOO) notifications
You can set up automatic vacation responses to let people who email you know when you're away from your mail. But you need to do this in your Gmail web interface, not using Outlook's Out of Office feature (which doesn't work with GSSMO).
Learn to use the vacation responder
You can set up contact delegation in G Suite, where an assistant can access and manage a supervisor's personal contacts. However, you can't do this in Outlook. Instead, you set up contact delegation and access a supervisor's contacts via the G Suite web interface.
Recalling a sent message
In Outlook, you can choose Recall Message from a sent message's Other Actions menu, to try to recall a message you just sent. However, unlike Microsoft Exchange, Gmail can't recall messages. Instead, the recipient receives both the original message, along with a follow-up message saying you wanted to recall the message.
Setting importance levels for recipients
In Outlook, you can send mail marked as "Important" or "Low Priority." But these values aren't synchronized with your G Suite account in the cloud and therefore don't show up for other users.