>>Sergey, thanks for the formula. One last thing: I wonder if the SMTP overhead is important to take into account for small messages.
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>Hi Javier,
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>The SMTP overhead depends on how fast/slow your SMTP server is. However I don't think you need progressbar for small messages at all. It's more annoying than helpfull.

Thanks again for your answer. I want to display a progress bar because is an indication that something is happening. Sometimes the connection to the SMTP server can take a few seconds and you that users start clicking and hitting everything when nothing appears to happen. Other solution would be to use WAIT WINDOW, but the progress bar is more consistent with my interface (and besides I'm not a great fan of WAIT WINDOW as it is not part of the common windows interface).