Hi, total Linux noob. Using Kontact and trying to setup Kmail.

I am trying to use my Zoho emails. When I input the info, I get this popup, "SECURE YOUR COMMUNICATION", select Key for this account, Loading keys, etc.
I have no clue what this is. I previously used Thunderbird Windows and it secures your email with the proper security settings automatically. You just choose SSL, TLS, etc. What is Kmail referring to here? I can't find any info on these questions anywhere.

I bypassed this on one email account and it seems to work. HOWEVER, I am very concerned there is no security now for these emails. This will be a work account for like 10 emails. Is there no security or encryption for KMAIL? I really can't have these emails messed with.

Is Thunderbird Windows more secure than Manjaro KDE KMAIL? Should I just dump Kmail for Thunderbird for security reasons? I am just playing around with Linux.

Thank you.