I've used WLM for some years and recently when sending to contacts on a mailing list of 87 people, I receive this error.  The message goes into the outbox and stays there.  I've sent to many more recipients in the past without problems.  I would use WLM 2012 but that too has issues with keeping contacts in category lists, thus I'm using WLM 2011.

Can anyone tell me why this is suddenly happening and how to resolve it?  I've tried suggestions I have found on the net such as:

unchecking 'My server requires authentication'

going into setting and checking 'log on using'

but other errors present themselves.

Thanks

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