email with password: user receives nothing

There are no active filters.
Sender and recipient are different.

This is the strange thing. The "Sender" account receives the messages from ProjeQtor because I see them in the "Sent" folder. Which means they were sent as well, but they never arrived. In my opinion it is Google that rejects the message, but since there are no errors I don't know what to check.

If I send an email from another Web Application (OSTicket), the mail is accepted by the "Sender", sent and received by the "Recipient".
Evidently with ProjeQtor there is something that does not allow delivery.

Hi Guys,
Same issue for me using gmail smtp..
I would really be happy if I could learn how to setup the latest phpmailer version into my SaaS server.
Any idea?