Email sending failures often stem from connectivity issues, incorrect server (SMTP) settings, or large attachments that exceed size limits. First, ensure that your internet connection is stable; if you're having trouble connecting, sending will likely fail. Next, check your email client's SMTP settings. You can usually find these in the settings under 'Outgoing Server.' Ensure the SMTP server address, port number, and encryption type (SSL/TLS) match the requirements of your email provider. Larger attachments may also prevent emails from sending; try compressing files or sending them through cloud storage services if they exceed limits. For web-based email clients, clear your browser cache and cookies, as corrupted cache data can hinder functionality. Temporarily disabling any email filtering or antivirus software can also be helpful, as these programs sometimes block outgoing mail. Contacting your email provider or checking their website for current status updates can also identify if they’re experiencing temporary server issues.