Office 365 SMTP: Setup and Configuration Explained

Microsoft 365, formerly Office 365, includes an SMTP service for sending email through applications and email clients, distinct from the free Outlook SMTP service and its narrower scope. Common uses include transactional messages, application notifications, event reminders, IoT alerts, client-based sending, and limited targeted marketing. Microsoft offers SMTP AUTH client submission, direct send, and SMTP relay, with SMTP AUTH presented as the simplest and most flexible option because it supports external recipients and OAuth 2.0; setup generally requires enabling SMTP AUTH and using smtp.office365.com with TLS and port 587 or 25. The guide also outlines configurations for WordPress, PHP, and Thunderbird, describes POP3 for local email downloads and IMAP for synchronized server-based access, and addresses issues involving authentication, blocked ports, sender permissions, timeouts, and TLS version requirements. It notes that Microsoft 365 SMTP has subscription costs, recipient and message-rate limits, limited bulk-mailing suitability, minimal monitoring features, and a potentially steep learning curve, while presenting Mailtrap as an alternative for high-volume sending, analytics, and developer-oriented email delivery.

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