No DKIM with outgoing email in Thunderbird

No DKIM with outgoing email in Thunderbird

Hello,

When I send my emails using Thunderbird , the outgoing emails (sent with smtp.zoho.com) aren't signed with DKIM. 

In the Zoho control panel DKIM is enabled and works fine. When I use Zoho webmail DKIM is sent with the mail. So apparently Thunderbird is the reason.

I use Thunderbird 52.6.0 , mail.strictly_mime = true , text encoding outgoing email = unicode UTF-8

Does anyone know how to fix this problem?

Thanks!