As a non-native English speaker, I have written a mail which contained a sentence that began as follows =

"For to proceed ahead we need to know what...... "

Have I made a grammatical blunder by writing "for to" or is it acceptable? I wrote it thinking it expressed the same meaning as "in order to" ...

Yes, I think you may have made a mistake, although the meaning is clear. You just need to write "To proceed we...." (i.e. you don't need the words "for" and "ahead").

As far as i know after preposition we generaly use gerands. So, when for is used the sentence should be: for proceeding we ...
or as mentioned before: to proceede we ...