Trouble using Sent to Mail - Tag Only

Hi everyone,

I was very happy when Calibre introduced the Sent to Mail - Tag Only Rule.

The problem that I noticed is that it only works when the format option is the default one.

For exemple: my brother only reads PDF format, so when a Periodical is created using the MOBI default, Calibre does not send him an automatic email, even when the Tag Only rule is fit.

Do you know how can I fix it?

thanks