I could remit it by mail transfer.

我还是将钱通过信汇寄过去吧。

We send the mail transfer by airmail.

我们通过寄航空信件来办理信汇。

A mail transfer agent such as Sendmail 8.7 or later.

一个邮件传输代理，比如Sendmail 8.7或者更高的版本。

I will explain for you. The other two are mail transfer and demand draft.

我来跟您解释，其余两种是信汇和票汇。

E-mail is sent via mail transfer agents, mail delivery agents, and mail user agents.

电子邮件通过邮件传输代理、邮件发送代理及邮件用户代理发送。