英文贺卡是表达祝福和感激之情的重要方式之一，其格式通常包括以下几个要素：

1. 问候语：常见的问候语有“Dear”、“Hello”、“Hi”等。根据收件人的关系和称呼，选择适当的问候语。

2. 开场语：开场语通常用于表达祝福或感谢之情。例如：“I hope this card finds you well”、“Thank you so much for…”等。

3. 正文：正文是贺卡的主要内容，可以在其中表达自己的心意、祝福或感谢。需要注意的是，要用简洁、明了的语言表达，避免过多的废话。

4. 结尾语：结尾语通常用于表达再次祝福或感谢，例如：“Best wishes”、“Take care”、“Thank you again”等。

5. 签名：签名是贺卡的最后一步，需要写上自己的名字，以示真诚。

以下是一份英文贺卡的范文：

Dear John,

I hope this card finds you well. I just wanted to take a moment to thank you for all your help with the project. Your hard work and dedication really made a difference, and I couldn't have done it without you.

I'm so grateful to have you as a colleague and friend, and I look forward to working with you again in the future. Best wishes to you and your family.

Take care,

Jane