在撰写留学英语邮件时，开头应该使用适当的问候语，以显示礼貌和尊重。以下是一些常用的开头方式：
正式场合
`Dear [Recipient's Last Name],`
`To whom it may concern:`
`Dear Sir/Madam,`
半正式场合
`Hello [Recipient's Last Name],`
`Hi [Recipient's Last Name],`
`Greetings, [Recipient's Last Name],`
非正式场合
`Hi team, `
`Hey guys, `
根据关系远近
`I hope you are well.`
`Have not heard from you for a long time, hope everything is going well with you.`
`How have you been recently？`
如果知道收件人性别或职称
`Dear Mr./Ms./Dr. [Recipient's Last Name],`
如果不知道收件人姓名
`Dear All, `
`Hi everyone, `
记得在问候之后，简要说明邮件的目的，这样可以让收件人迅速了解邮件内容，提高沟通效率。