SendGrid with Flask: Flask-Mail SMTP config

TL;DR: Configure Flask-Mail to send through SendGrid's SMTP relay: the five MAIL* settings, the literal apikey username, and keeping the key in the environment. MAILDEFAULT_SENDER must be a verified sender.

The fix

app.config.update( MAILSERVER='smtp.sendgrid.net', MAILPORT=587, MAILUSERNAME='apikey', # literal string, not your key MAILUSETLS=True, MAILDEFAULTSENDER='[YOURVERIFIED_SENDER]' # verified sender )

Set MAILPASSWORD from the SENDGRIDAPI_KEY environment variable (for example via os.environ when building config). Do not hardcode it.

Then:

from flaskmail import Mail, Message mail = Mail(app) msg = Message('subject here', recipients=['[RECIPIENTEMAIL]']) msg.body = 'plain body' mail.send(msg)

Checklist:

1. MAIL_USERNAME is exactly 'apikey'.
2. MAILUSETLS True with port 587. Port 465 wants MAILUSESSL instead.
3. MAILDEFAULTSENDER must be a verified sender.
4. In tests, suppress sending (MAILSUPPRESSSEND) or point at sandbox mode so CI stays quiet.

When to use this

• This covers exactly what the title says: SendGrid with Flask.
• You are setting this up for the first time, or auditing an existing setup.
• You want the key gotchas in one place before you start.

When not to use this

• You are doing a different workflow with SendGrid; these steps are specific to the title above.
• You need the full reference docs; this is the short path, not the manual.

Compatibility

• Not pinned to a specific version; follows current SendGrid behavior.

Flask-Mail reads MAIL_* config and speaks SMTP; the SendGrid-specific facts are the official SMTP settings: host smtp.sendgrid.net, literal apikey username, port 587 with TLS. Sources: https://github.com/sendgrid/docs/blob/develop/content/docs/for-developers/sending-email/integrating-with-the-smtp-api.md