The spamdyke documentation says for TLS:
With no TLS options given, spamdyke will identify a TLS conversation and simply pass the data back and forth between qmail and the remote client. In this mode, spamdyke cannot read the SMTP data (obviously – it's encrypted). This prevents some of its filters from functioning, including graylisting, sender and recipient blacklisting, limiting the number of recipients, checking the sender's domain name for an MX record and relaying.
Thus, if you want to use these features from spamdyke, eQmail TLSREQUIRED variable doesn't have to be set.