We first change the problem a bit, and deal with the word marMalade.
List the vowels in their original order: a a a e. They determine $5$ "gaps" (we are counting the space before the first a and the space after the $e$ as gaps).
Now look at the letters m r M l d. The first of these, namely m, can be slipped into any of the $5$ gaps. After we do that we have a $5$-letter words, i.e. $6$ "gaps." The letter $r$ can be slipped into any of these $6$ gaps.
Now we have a $6$-letter word, that is, $7$ gaps. We can slip $M$ into any of these. Continue. We end up with $5\cdot 6\cdot 7\cdot 8\cdot 9$ "words."
Now turn the M back into an m. This divides the number of words by $2$. Thus the total number of words for the original problem is $$\frac{5\cdot 6\cdot 7\cdot 8\cdot 9}{2}.$$
There are many other ways to solve the problem.