>>>Hi,
>>>
>>>Currently my application sends emails via SMTP of the client (work station). A customer is asking me if I could change the program and use SMTP of a server? Is it possible?
>>>
>>>TIA.
>>
>>How do you use it on LOCAL?
>>SMTP is a Server.
>
>Yes, of course, you are right. Let me describe the problem. And some of it I don't quite understand but I am sure you will. The customer tells me that they want to use DHCP to get IP address dynamically (on client PCs). But they say that they cannot do it because of my application. Supposedly, if I understand correctly, the SMTP is somehow "tied" to IP. And if IP of the machine changes, the SMTP cannot be used. Therefore for PCs that use my application they have to assign static IPs. Does it make sense?

No.
That didn't make sense to me :-)
The SMTP Server should be something like:

mail.domain.com
test.domain.com
etc.
That server address has noting to do with the local IP.

When you setup Outlook Express to send mails did you change it every time you change your local IP?