My Quick Mail WordPress plugin sends emails with attachments from WP Dashboard or command line with WP-CLI. Quick Mail 4.0.5 lets administrators block recipients.
WordPress 5.6 includes jQuery 3 – first jQuery update since 2016. Send email from WP with Quick Mail, without jQuery warnings.
Quick Mail 1.2.2 includes dismissible messages and a responsive form design. Tested with WordPress 4.2.3.