Have you tried to send an email but failed because it is thought to be spam? The Bluewin server checks emails to see if they resemble spam in order to prevent unfair mass advertising. An email suspected of being spam will not be sent, and a message to this effect will be received by the sender.
If your email is falsely classified as spam, please consider the points listed below in order to increase the chances that your emails can be sent.
If there is a link to a website in your email, run a check without it and send it again. Links to websites are often the reason that an email is suspected of being spam. If a link is listed as spam, no further emails containing it can be sent.
The likelihood of an email being classified as spam is increased when images it contains embedded images which can be opened without being accessed online. Delete any unnecessary images embedded in the email.
A signature containing suspicious elements can mean that emails with this signature are blocked. The two most problematic elements of signatures, hyperlinks, and embedded images have been described above. Change or delete your signature, and try to send the email again.
Try to send your emails without attachments whenever possible. Cloud services such as Dropbox are alternative ways of sending files to be shared by the person receiving the mail.
Using the "Reply" or "Forward" links the previous emails to your message and the length of the email continues to grow. This increases the likelihood of an email containing typical spam features. So if you can't send an email using Reply or Forward, create a new message which has no pre-existing content. Copy the relevant contents in, and try to send the email again.