phpBB supports sending email over SMTP. To have phpBB relay email through SendGrid go to Client Communication > E-mail settings in the admin panel and change:
- Use SMTP server for e-mail - Yes
- SMTP server address: - smtp.sendgrid.net
- SMTP server port - 587
- Authentication method for SMTP - PLAIN
- SMTP username - sendgrid_username
- SMTP password - sendgrid_password
The following image shows these settings.