You can just pick up the telephone and ask. Although you can ask that you be emailed or faxed a copy of the proof of service indicating when service was perfected on you, the important thing is to ascertain the date and manner you were served.
Regardless, you can always come to an agreement with the plaintiff's counsel on a date certain as to when your answer or responsive pleading is due.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult with your own attorney.
Just call his office and ask for him. You'll probably get his secretary or paralegal. Ask that you be emailed or faxed a copy of the proof of service indicating when service was perfected on you. No letter, certified or otherwise is required.