Trojan or Virus on my G5? SMTP Server denial

I just discovered yesterday that I had nearly 50 e-mail messages in my outbox, in the Mail program native to OS X. No wonder people were asking me where I had gone and why I was not responding to them. It turns out my SMPT servers are refusing to work.

So, I sent an address list a note, or attempted to do so through a much less used e-mail account set up in Thunderbird. And what did it do? Same problem, could not send out due to SMPT issues as well.

Then, this morning, I remembered that a few weeks back there was some nefarious thing that installed on my computer, within about 2 seconds the thing had broadcast it's progress bar on the screen, much too fast for me to detect what it might have been. It was not something I'd ever witnessed on this computer before. I suppose I've got a virus or trojan. Now my question would be, how do I find out from the Activity monitor which of the processes it might be and kill the thing?

On my PC about 5 years ago I got a virus that keylogged everything I did for two weeks, and Norton Anti-virus did not pick it up. I worked with the guys from Techguy.org for those two weeks and we finally detected the thing and killed it. They informed me that it was "network aware" and would move itself around to different folders. After we killed it's process and deleted it, we then found it's text document recording all user actions and keystrokes on the computer.

One of those tech guys sent the thing in to Symantic Corp. (Norton Antivirus) and they responded they had not had anything that sophisticated before, nothing even in beta testing yet to detect such a trojan.

Does anyone have any suggestions for me? I don't need to go refigure SMPT settings, I've been through that enough now, and both e-mail accounts in two different programs don't all of a sudden need to be reconfigured, this I'm sure is a virus or trojan issue, don't you think?

And just so you know about the attachment, the drop down menu on the screen shot says "mail.comcast.net" but my settings are set to "smpt.comcast.net" as it always has been.

Comcast is only one program. And what of the other e-mail program with another e-mail account not even associated with comcast?

Plus, I've already been on tech support with comcast, nothing found, and nothing discovered on why I can't get out through other e-mail accounts including the one through Thunderbird.

The ISP the guilty party here

I appreciate all of your help.

I took that first suggestion and checked if my ISP (comcast) had marked my address as a spammer. Though I'd already been on tech support with them, this round I specifically asked them if I had been targeted for that reason. They affirmed it so. The very last e-mail message I sent out was to the leaders in my local precinct who I was informing them how I wished them to vote in the convention. I got suspicious that indeed one of them might have been opposed to my views and had spite enough to turn me in as a spammer. I didn't get Comcast to admit to such a thing, but I was given a case # that I can check on---the specific case that marked me as a spammer.

At any rate, I thank you for the tip here, even though I thought it was a virus and trojan because I had seen a quick "install" of something a few weeks ago, or an unzipping of something that I did not initiate, plus the problem of the other e-mail address---I suppose just a coincidence of both failing at the same time.