SMTP Connections

SendGrail manages email delivery through SMTP connections. You can configure multiple connections for different providers and switch between them as needed.

Creating a Connection

To create a new connection, navigate to Connections and click Add Connection.

Provider Selection

Start by selecting your email provider from the preset list. Provider presets automatically fill and lock provider-specific fields such as host, port, and encryption method, reducing configuration errors.

If your provider is not listed, select Other / Custom SMTP to manually configure all fields.

Connection Fields

Field	Description
Host	SMTP server hostname (e.g., smtp.gmail.com)
Port	SMTP port (typically 587 for TLS, 465 for SSL, 25 for none)
Encryption	TLS, SSL, or None
Authentication	Whether the server requires authentication
Username	SMTP username (often the email address)
Password	SMTP password or app-specific password
From Email	The sender email address
From Name	The sender display name

TIP

When using Gmail, you must generate an App Password from your Google Account security settings. Your regular Gmail password will not work with SMTP.

Editing a Connection

When editing an existing connection, the password field displays dots to indicate a stored value. If you leave the password field unchanged, the existing password is preserved. Only enter a new value if you intend to change it.

Enabling and Disabling Connections

Each connection can be individually enabled or disabled. A disabled connection will not be used for sending emails, even if referenced by a routing rule.

WARNING

The default connection cannot be disabled. To disable it, you must first set a different connection as the default.

Setting the Default Connection

One connection must always be designated as the default. The default connection is used for all outgoing emails unless a routing rule directs the email to a different connection.

When you set a connection as the default, any previously designated default connection is automatically deactivated from that role.

Testing Connections

SendGrail provides a raw SMTP socket test to verify that a connection can communicate with the mail server. The test performs the following steps:

1. Opens a socket connection to the SMTP host and port
2. Sends the EHLO command to identify the client
3. Initiates TLS encryption if configured
4. Performs AUTH with the provided credentials

This test validates the connection at the transport level without sending an actual email. Use the Test Email feature to send a real message.

Connection Health Table

The connections list displays health information for each configured connection:

Column	Description
Status	Current connection state (active, inactive, error)
Last Tested	Timestamp of the most recent connection test

Per-Connection Statistics

Each connection tracks its own delivery metrics:

Metric	Description
Sent Today	Number of emails successfully sent in the current day
Total Sent	Lifetime count of emails sent through this connection
Fail Rate	Percentage of failed deliveries relative to total attempts

These statistics help you monitor the reliability of each provider and identify connections that may need attention.

Password Encryption

All SMTP passwords are encrypted at rest using AES-256-CBC encryption.

By default, SendGrail uses the WordPress AUTH_KEY constant as the encryption key. For enhanced security, you can define a dedicated encryption key by adding the following to your wp-config.php:

define('SENDGRAIL_ENCRYPTION_KEY', 'your-secure-random-string-here');

DANGER

If you change or lose the encryption key, all stored SMTP passwords become unreadable. You will need to re-enter the password for every connection.

TIP

The SENDGRAIL_ENCRYPTION_KEY takes precedence over AUTH_KEY when defined. Use a strong, random string of at least 32 characters.