Atache a number to each email

Hi, Everybody:

When autorespond to emails received, is there anyway to atache a 
consecutive number to it? Say:
1. For the first email received on 02/12/96, Procmail responds with:

Email number: 02129601
Other autoreply text.

2. For the second email received on 02/12/96, Procmail responds with:

Email number: 02129602
Other autoreply text.

................

etc.

Thanks in advance.

JZ