I have to open each and every message on the
workstation and hit the "Send" button manually.

Even with a send/receive interval defined?

Yes, it looks like not all messages that sit in Outbox are sent out
when Send/Receive is initiated. Such message must be also marked to be
sent somehow, and the only way to do it is to open it and hit "Send".
Messages that are "marked to be sent" from Outbox are shown in italic,
the others are shown in plain text.

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Blumidoo