Null byte in data when sending attachments

I'm using NS 7.2, Win XP Pro and have a cable connection thru Comcast.net. When I try to send an attachment (usually Word, but sometimes occurs with Excel attachments) to an email message, I get an error message saying the server responded: null byte in data. This seems to only happen with a direct connection with Comcast. It doesn't happen when I use their webmail service, and it doesn't happen using NS 4.7 or Outlook or Eudora. Comcast is unresponsive because they say they'll only support Outlook. I've looked on the web and seen several people with similar problems that have been solved by changing outgoing server settings, disabling AV programs, etc. I've tried all those--disabling AV, disabling firewall, etc., all to no avail. Any ideas?

 

I am afraid that you have a number of strikes against you. Comcast, and Word or Excel attachments.
I have Cox, and I use Open Office which converts Word or Excel files, and, have had no problem with them. come to think, I was able to send at least one .doc attachment.
I suggest that you zip one file, as a test, and send it in that form.

 

Well, perhaps, but that doesn't explain what the problem is or how to correct it. At one time, all worked fine. It also doesn't explain why it only happens with the Comcast/NS 7.2 combination. It doesn't happen with other email clients (Eudora, Outlook, NS 4.7 Messenger) or another ISP (pacbell.net).

 

One explanation is that Comcast started authentication. I don't believe that it was like that all the time. But, I don't have Comcast, and if contact them you may get a "duh?" for an answer. Also, some not so open minded ISPs have finally discovered that 7.1 exists. I have had to use the user profile switcher in some cases, while in 7.2, faking 7.1. However, if you authenticate, you may not be able to get away with it.
But, I am just guessing. Did you try to send the files zipped, as I suggested?

 

Yes, it sends the zipped file ok. But who wants to zip a file every time?

 

If it worked with the zipped file, and there is no problem with other ISPs, the answer is pretty obvious.

 

Not so obvious to me, other than a problem with Comcast. The question is, can anything be done about it? It doesn't happen with other computers using the same OS and NS 7.2 and Comcast.

 

This is the first time you said that. Ok, I don't know.