another way would be to create a two-line envelope
(where the tilde is at the left margin):

  ~r testfile1
  ~r testfile2

and then send that:

  mail -I abc@add.net < envelope

>to: peter wu <peterwu@fenix2.dol-esa.gov>
>fr: john abreau <jabr@blu.org>
>su: re: mail , mailx
>dt: fri, 3 aug 2001 16:57:42 -0400 (edt)
>
>On Fri, 3 Aug 2001 Peter Wu <peterwu@fenix2.dol-esa.gov> wrote:
>
>> Hello,
>>    I am using mail command trying to send two files from unix
>>    Say, mail abc@ddd.net < testfile will send testfile to abc@ddd.net
>>
>>    Is there a possibility  to send two files at one time
>> lide mail abc@ddd.net < testfile testfile2
>> I tried this line of command but it always gave me error message
>> So, Do you have any idea how i can send two files at one time
>>
>>
>> my system is Dynix/ptx
>
>Mailx predates the MIME standard, and thus it doesn't attachments. If you
>wanted to send multiple files with mailx, you'd have to first combine them
>into one file. A common convention is to use "tar" create a combined file,
>"gzip" to compress that file, and "uuencode" to clean it up for the mail
>system.i (image attachment)