英語で「待たせて申し訳ない」とメールするには？

申し訳ございません

• My apologies for the delayed response. I am sorry to have kept you waiting.

もう少しカジュアルな表現

• Sorry for the delay in getting back to you.

一般的な表現

• I hope this email finds you well.
• Thank you for your email.
• I appreciate your patience and understanding.

締めくくり

• Please let me know if you have any further questions.
• I look forward to hearing from you soon.
• Thank you for your time and consideration.