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