X-ZohoMailClient: External footer

X-ZohoMailClient: External footer

Hi!

I've recently registered my domain here so I can use custom email addresses for my automated projects.
One thing I've noticed, which is a bit irritating, is that when I send an e-mail via sSMTP from linux, it places a line "X-ZohoMailClient: External" at the end of the message. I'm not yet familiar with the working of a complex mailing system, but I found that I might need and app password for automated mailing scripts, but unfortunately I couldn't find the option to set one.

Can you help me with either finding the place to set up app passwords or at least removing the last line from the message?

Tanks in advance,
Ben Party