SMTP Configuration
Host: smtp.gmail.com, Port: 587 (STARTTLS) or 465 (SMTPS).
Use App Password (2‑Step Verification required). From must match account or allowed alias.
Host: smtp.office365.com, Port: 587 (STARTTLS). SMTP AUTH must be enabled for the mailbox.
Yahoo: smtp.mail.yahoo.com (465 SMTPS, App Password). Zoho: smtp.zoho.com (587 STARTTLS or 465 SMTPS).
Timeout = port blocked by host or firewall. Try 587 or 2525. Use server hostname matching SSL certificate.
535/534: wrong password or provider requires App Password. Ensure SMTP AUTH is enabled on mailbox.
Check SPF/DKIM/DMARC. Use a From domain you own. Avoid port 25 on consumer ISPs.