Which activity must be used to send an email using SMTP in UiPath?

To send an email using SMTP in UiPath, the SMTP Mail Activity is specifically designed for this purpose. This activity facilitates the connection and communication with an SMTP server, allowing users to send emails as part of their automation workflows. It requires you to configure parameters such as the SMTP server address, port number, and authentication details, making it a robust choice for handling email transactions within an automation project.

The other options do not provide the necessary functionality to send emails via SMTP directly. For instance, the Send Email Activity typically uses higher-level protocols such as Outlook or other integrated email services instead of directly interfacing with SMTP servers. The Email Sender Activity and SMTP Connector, while they may sound related potential options for sending emails, don't specifically address the requirements for sending messages over SMTP in UiPath's framework. Hence, the SMTP Mail Activity remains the correct and most effective choice for this specific task.