If you have received an error "The operation timed out waiting for a response from the sending (SMTP) server" when you are using a POP3 account with SSL to send SMTP e-mail from Outlook.
The symptoms are:
If you send a Simple Mail Transfer Protocol (SMTP) e-mail message by using Secure Sockets Layer (SSL) and a Post Office Protocol version 3 (POP3) account, you may receive the following error message:
'Sending and Receiving' reported error (0x8004210B): The operation timed out waiting for a response from the sending (SMTP) server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP). The message remains in the Outbox.
The cause is:
This behavior may occur if the e-mail account is damaged.
The solution for this error is:
To resolve this error, remove and then re-configure your e-mail account.
Follow these steps to re-configure email account:
Click Start, point to Settings and then click Control Panel.
Double-click Mail, and then click E-mail Accounts.
Click the e-mail account name, and then click Remove.
Re-create the e-mail account.
For additional information about configuring an e-mail account and for this kind of behavior, you can refer below link as this link is the source of article: