Urgent!!! PO/Sales Orders/Invoices are not attaching to emails

Urgent!!! PO/Sales Orders/Invoices are not attaching to emails

Today we have an issue with attaching generated pdf's to any emails. Everything looks fine and we are getting "successfully sent" message after sending email as well as generated pdf file name on the right. But receiver do not getting any attachment.
It brought so much mess today in our work process.

Did anyone else experience the same issue?