What is the ruling on dialogue between the two sexes for the purpose of Dawah or otherwise, given the conflicting fatwas regarding this?

Dialogue between the sexes is permissible in the call to Allah (Da‘wah), provided that the শরী‘আ (Sharia) guidelines are observed, such as not speaking in a soft or alluring manner. As for the advice to avoid dialogue with a non-mahram woman online, it is not a prohibition but rather a recommendation due to potential risks, such as illicit uses and the possibility of temptation (fitnah).