Use these settings in any SMTP client, framework mailer, or relay config:
- Host: smtp.sendgrid.net
- Username: the literal string apikey. Not your account email, not the key name. This is the number-one misconfiguration.
- Password value your SendGrid API key (needs at least Mail permissions). Paste it carefully: no trailing newline or whitespace, because SMTP is line-oriented and stray linefeeds break auth.
- Port: 587 with TLS (recommended). 25 and 2525 also work for TLS/unencrypted; 465 is for SSL.
Limits: 5,000 messages per SMTP connection, and 10,000 concurrent connections from a single server. If you send bulk, reuse connections instead of opening one per message.
SMTP is the right call when a framework already speaks SMTP (Django, Laravel, Rails, Flask-Mail) and you do not want an SDK. Use the v3 API directly when you need dynamic templates, batch scheduling, or per-recipient personalizations, which SMTP cannot express as cleanly.