Why do I get this message when replying to posts?

Recently when replying to posts in this forum, after I hit 'Send' the system gives me the following message:

[color=blue:a60c87f924] Ran into problems sending Mail. Response: 503 Bad sequence of commands

DEBUG MODE

Line : 193 File : smtp.php [/color:a60c87f924]

I've found that my reply does get onto the forum as it should, so maybe this message isn't a big deal. But does anyone know why it comes up at all?

It is a bug in the forum system. We have tried to fix it a few times but it seems to hide whenever we get close. The forums messages are posted though.

Rober, I read this earlier. A thought has just occurred to me. Please read the post I just made in the Plato subforum. It is also my experience that posts I make do invariably get posted when I encounter this error. It is also also my experience that I frequently find myself prefacing a post with words like 'Sure I posted about this before but' ...

Is there any possibility that posts that encounter this error do get posted but do not persist?

By way of a test case, I have posted twice this morning, three times when I post this one. The first one, in the Support subforum, I encountered the error when I posted it. The second one, in the Plato subforum, I did not. This one ... well, I don't know yet!

I have had a look at the code that posts to the forum and made a few changes. If you see any more errors can you send the url to ftn95@silverfrost.com please.

The code that sends the emails run after posting to the forum so I don't think this issue could cause missing posts . Also it only runs on replies, not the initial posting so any starting post should be okay.