SOST background jobs

Hi,

We have one background job scheduled everymonth. After ruunning, it has to send the report to 2 mail ids (Outlook) that are in the distribution list.

When i see the status in <b>SOST</b>, it says the message is not sent and shows the following error messgae no <b>829</b>

<b>Internal error: CL_SMTP_RESPONSE ESMTP error code is not

known. 554 554 5 3.4 Message size exceeds fixed maximum messa</b>.

Anybody can call what is wrong with it ?