a. Check size attachment
· Go to the Outbox folder in your Outlook and move the message to the Drafts folder. You can either drag the message to the Drafts folder or you can right-click the message, select Move, select Other Folder, and then select the Drafts folder from the list.
· Then, open the specific email with the large attachment accordingly. Then, try to resend the email.
b. Send / Receive folders
· In Outlook go at the top find Send / Receive tab and click Send / Receive all folders
c. Restart Connection
· In Outlook main screen, go at the taps menu and find Send / Receive tab, Then, click Work Offline
· Click again Work Offline
d. Clear drafts / deleted items
· Go to Deleted items in your Outlook, and click CTRL + A from the keyboard
· Then press the Delete button from the keyboard to delete all emails
· Repeat the above steps for drafts folder