We are trying to get meeting invites to send out and every time they try to send we get the following errors in the log file:

Wed Oct 26 14:50:16 2011 [4483][1][FATAL] SMTP -> ERROR: Failed to connect to server. Code: 111 Reply: Connection refused
Wed Oct 26 14:50:16 2011 [4483][1][FATAL] SugarPHPMailer encountered an error: SMTP Error: Could not connect to SMTP host.
Wed Oct 26 14:50:16 2011 [4483][1][FATAL] SugarPHPMailer encountered an error: An outgoing mail server is not configured to send emails. Please configure an outgoing mail server or select an outgoing mail server for the mail account that you are using in Settings >> Mail Account.

Our mail servers are set up, and the test email and normal emails send fine from the server. Is there something within the setup for meetings or files that need to be amended? I've tried everything and am running out of ideas and at my wits end!