I submitted my paper by e-mail one week ago. How long is it reasonable to wait for the receipt acknowledgement? What to do if they won't acknowledge receipt of the paper?
Most journals work with electronic submission systems but some still work with manual handling. Regardless, both systems require a person to handle the manuscript once it arrives. Since the past week has been the Christmas holiday for many and persons working with journals such as editors are usually not employed to work with the journal but do it aside their regular job, it is not strange that not much will happen during the holiday season.
I am sure you will receive notice of your submission sometime in the next couple of weeks into the new year, once the persons responsible will have a chance to have a look.
As a side note, as an editor, I can see that the number of submissions is slightly increasing before summer (holidays) and Christmas/New Years (holiday season). Authors, naturally, want to get their works away before taking time off, unfortunately, editors and reviewers, naturally reluctant to take on reviews during the holidays, do the same so the increased flux of manuscripts creates something of a traffic jam at these times. From this perspective, submitting a manuscript away from these times of the year will likely result in, at least slightly, faster response and turn-over times.
You don't mention when the deadline is. If the deadline is a good two months away, waiting a week or so is nothing to be alarmed about.
Moreover, you've asked this question on the week between Christmas and New Year's – a time when many offices resemble ghost towns. Given that New Year's Day falls on a Thursday this year, I'm guessing it's sitting in someone's inbox, and there's a good chance it will remain there, unread, until Monday, January 6th. Even then, there may be a backlog of email and other submissions, so give it another week after that.
If the person responsible for reviewing submitted papers works in academia, there's a chance it might even go longer than that, depending on their institution's academic calender. (In other words, they might not get back into the full swing of things before the semester begins.)