Emails sent in client Windows Live Mail 2012, whilst going into sent folder,  are not being received by recipients unless there is an attachment.

I have checked that sending emails, whether with or without attachments,  direct in service provider's email page does work so this would point to a Live Mail being source of problem.

I have not changed any settings in Live Mail. I did do some maintenance work such as deleting newsfeeds quite recently.

I would appreciate some help to solve this problem.