Wrong Content-type pdf format

Hi, we have a problem with viewing the pdf documents emailed with Post SMTP Mailer/Email Log, in the management of tickets using the platform Liveagent.com.

When a new ticket arrives in the Liveagent dashboard from a customer, we can normally preview a pdf without having to download them. This happens with all pdfs but NOT with those emailed as an attachment by your plugin. The Liveagent support says pdf normally have Content-Type = application/pdf; while those emailed with pPost SMTP appear as Content-Type: application/octet-stream.

Liveagent also says “The application which is sending the email is responsible for setting content-type header of the attachment, LiveAgent just reacts (displays “View” option or not) according to the value found in email.” https://support.liveagent.com/715429-The-View-button-availability-for-attachments-in-tickets

To be precise we use Post SMTP with “Type = SMTP” and “Mailer Type = PostSMTP”. We don’t know why but “Mailer Type = PHPMailer” doesn’t work.

Any ideas to solve this issue?
Thanks