You may want a signature for internal mail and a different one for external mail.

您可能想对内部邮件使用一个签名，对外部邮件使用另一个签名。

youdao

Managed the internal and external mail functions.

处理内部和外部邮件。

youdao

In his statement Thursday, Ryley said Sky News had commissioned an internal audit of payment records, alongside the external review of e-mail records.

CNN: UK broadcaster Sky News admits e-mail hacking

At more than 250 GB, it would have to be sent on an external hard drive by regular post -- snail mail -- for any independent scrutiny.

CNN: Computer spyware is newest weapon in Syrian conflict

TeleCruz designs a system-on-a-chip that equips a TV set's innards with modest e-mail and Web capabilities without the need for fancy external electronics.

FORBES: Cruz Control