写一封留学生教授的信，无论是推荐信还是感谢信，都需要遵循一定的格式和礼仪。以下是一些基本的步骤和要点：

选择合适的称呼

对于初次联系的教授，使用“Dear Professor [姓氏]”较为正式。

如果已经建立了联系，可以使用“Hi”或“Hello”来显得更亲近。

简洁明了的邮件主题

使用一个简洁、明确的主题，避免使用模糊的主题如“Hello”或“Urgent”。

开门见山，表明邮件目的

在邮件的第一段中直接说明发送邮件的目的，例如申请加入教授的研究团队、感谢教授的悉心指导等。

提供必要的背景信息

在邮件中适当提供背景信息，帮助教授回忆起你们之前的沟通内容，避免查找之前的资料。

清晰列出问题或需求

在学术邮件中，条理清晰是非常重要的。明确列出你的问题或需求，使教授能够快速理解你的意图。

礼貌的结尾

结尾应表达感谢，并留下联系方式，例如“Looking forward to hearing from you.”或“Best regards, [你的名字]”。

检查语法、拼写和格式

确保邮件无误后发送，避免语法错误和拼写错误。

```

Dear [Admissions Committee/Professor's Name],

I am writing to recommend [Student's Name] for admission to your esteemed program. As [his/her] professor during the [academic year/term], I have had the pleasure of witnessing [his/her] growth and academic achievements.

[Student's Name] has demonstrated exceptional [academic/research] skills, [his/her] dedication to [specific field/topic] is truly commendable. [He/She] consistently excels in [specific courses/projects] and has shown a keen interest in [specific research areas]. [His/Her] ability to [specific skills, e.g., think critically, work collaboratively, solve complex problems] makes [him/her] an outstanding candidate for your program.

I am confident that [Student's Name] will make significant contributions to your program and look forward to seeing [his/her] future accomplishments. Please feel free to contact me if you require any further information or insights into [his/her] qualifications.

Sincerely,

[Your Full Name]

[Your Position]

[Your Institution]

[Your Contact Information]

```

请根据具体情况进行调整，确保信件内容真实、准确、有针对性。