The other discussions I found did not give a clear answer to my question.
Problem description: I am running an embedded Linux server device, such as TuxRail or a DreamPlug which are ARM-based devices with very little of memory and using a micro-SD card as their mass memory device and don't have GUI frontends. They are running Debian Squeeze. I also have IP-cameras from D-Link which can send motion captures via email with SMTP-settings but which have bad limitations (such as that username-field cannot be over 20 characters(!)) and that is why I want to create my own SMTP/eSMTP-server into a separate Linux box which would allow these short usernames and then relay these emails forward to actual ISP's SMTP-server.
Question: What would be suitable "real" SMTP-server for such a Linux SBC box? Your answer is only worthwhile, if the server you suggest runs a daemon which acts as a SMTP server in TCP/IP port 25 and/or 465 and can relay those emails to similar ISP servers.
(Please don't suggest me something completely different from what I asked, I specifically want "IP-to-IP" kind of SMTP relay server, not commandline MTAs or anything like that since I don't have access to the commandline of that IP-camera product)
Thanks in advance!