When you send an email using LSP.expert, you can easily track its status (sending, sent, opened).
In the list of invoices and quotes, the icon of a small envelope automatically appears next to the date of issue of an invoice/quote when you change the invoice/quote status to 'Sent'. This envelope can be grey (email is being sent), light blue (email has been sent) or green (email has been read).
In the invoice/quote itself, you'll see the icon of a clock with an arrow around it next to the Date sent, which gives you the history of the email (when it has been sent, delivered and opened by every recipients). The Date sent will also be grey (email is being sent), light blue (email has been sent) or green (email has been read).