BUG REPORT: FluentSMTP SMTP2GO reads wrong wp-config.php constant - uses SendGrid constant instead

Problem Description:

When configuring SMTP2GO with FluentSMTP using wp-config.php constants, the official documentation states to use:

php

define( 'FLUENTMAIL_SMTP2GO_API_KEY', 'your-api-key-here' );

However, this constant does not work. When using the correct constant name as documented, FluentSMTP shows:

• Error message: "Credential verification failed. Check your input"
• Interface shows: "Define FLUENTMAIL_SENDGRID_API_KEY in wp-config.php file" (notice it mentions SENDGRID instead of SMTP2GO)

Workaround/Solution:

The actual working constant for SMTP2GO is incorrectly mapped to the SendGrid constant:

php

define( 'FLUENTMAIL_SENDGRID_API_KEY', 'your-smtp2go-api-key-here' );

When using FLUENTMAIL_SENDGRID_API_KEY with the SMTP2GO API key, the connection works perfectly.

Evidence:

• Same API key works fine when stored in database
• Same API key fails with FLUENTMAIL_SMTP2GO_API_KEY constant
• Same API key works with FLUENTMAIL_SENDGRID_API_KEY constant
• Error message incorrectly references SendGrid constant name

Impact: This bug causes confusion for users following the official documentation, as the documented constant name doesn't work, while an undocumented workaround is required.

Expected Fix: FluentSMTP should properly read the FLUENTMAIL_SMTP2GO_API_KEY constant for SMTP2GO connections, not the SendGrid constant.

Shahjahan Jewel - FluentSMTP bug: SMTP2GO reads wrong wp-config constant (SENDGRID instead of SMTP2GO). Please fix constant mapping in SMTP2GO module.