There are a few features G Suite Sync for Microsoft Outlook (GSSMO) does not support in Outlook mail. The GSSMO features aren't available in Outlook or might not work as you'd expect.
GSSMO features not in OutlookRecovering 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.)
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.)
GSSMO doesn't allow sending executable file attachments (including executables in compressed attachments) from Outlook or the Gmail interface.
Types of files that can't be sent from Outlook: .ade, .adp, .bat, .chm, .cmd, .com, .cpl, .dll, .exe, .hta, .ins, .isp, .jse, .lib, .mde, .msc, .msg, .msp, .mst, .pif, .scr, .sct, .shb, .sys, .vb, .vbe, .vbs, .vxd, .wsc, .wsf, .wsh
There are also limitations when you send .eml or .msg attachments to Outlook users. For details, go to Can't view MSG or EML files.
Delivery receipts aren't generated in Outlook when using GSSMO. If you request a delivery receipt for a message sent from Outlook, you won't receive a response when the message is delivered. Instead, you can request an Outlook read receipt.
Email encryption using S/MIME isn't supported when sending email using GSSMO. As a workaround, S/MIME works when set up using an IMAP connection.
If you're using a Gmail alias and have Treat as alias turned on, the alias appears in the To or Cc fields when you reply in Outlook. Learn more
Outlook features that are available, but might not work as expectedRead receipts
Read receipts are generated in Outlook with GSSMO. To get a response when your message is read, your recipient must be using Outlook and must turn on read receipts for their profile.
You can set up automatic vacation responses to let people know when you're away. You must do this in Gmail, not using Outlook's out of office feature (which doesn't work with GSSMO). Learn how to set up an out of office or vacation reply in Gmail.
You can set up contact delegation in G Suite to give other users in your domain permission to access and manage your personal contacts. This feature isn't available in Outlook. Learn how to Give another user access to your contacts.
In Outlook, you can choose "Recall Message" from a sent message's Other Actions menu to try to recall a message you just sent. Unlike 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.
You can send mail marked as "Important" or "Low Priority" in Outlook. If you do, these values aren't synchronized with your G Suite account in the cloud and don't show up for other users.
Office add-ins for Outlook installed from the Office Store are not supported because they require an Exchange account. These types of add-ins include the Google Meet add-in.