When choosing an SMTP server, consider the following factors: 1. Reputation: Opt for a server with a good reputation and positive reviews. 2. Uptime: Ensure the server has a high uptime rate to avoid interruptions in your email campaigns. 3. Speed: Faster servers ensure that your emails are delivered quickly. 4. Security: Look for servers that offer robust security features. 5. Customer Support: Good customer support is crucial for resolving any issues that may arise.