When am I supposed to get an acknowledgement for a paper submitted via e-mail (CS conference)? I have submitted a paper to a CS conference. Am I supposed to get an acknowledgement email, so I know it hasn't ended up in the spam folder by accident, and that it will be considered for the conference? If so, how long after submission? Is it OK to contact the conference organizers and ask if my submission has been received?
In computer science, paper submission by e-mail is non-standard. Therefore, there is no default answer to your question.

However, it's in the interest of the conference organizers to show good professional communication that does not leave authors "in the dark". I would expect them to confirm your submission immediately after submission, within 24 hours. If you have not heard back from them after 24 hours, it's absolutely OK to contact them.