All mail sent from the shared hosting services is sent via a spam-filtering outbound mail gateway. This is to protect the IP reputation of our servers, and therefore the deliverability of all emails sent by all of our customers from our cPanel and Plesk shared web hosting servers.
This mail gateway examines every email sent from the shared server, considers its contents, and applies a numeric ‘spam score’. When a mail’s ‘spam score’ exceeds a certain threshold, it is considered to be spam, and blocked.
When a mail you send is blocked by our mail gateway due to it’s recognising your email as SPAM in this way, you will receive a ‘bounce’ message, which may have a subject similar to:
Mail delivery failed: returning message to sender
It can be hard to make sense of the email headers which are included in these emails, but essentially what has happened is that some characteristics of the email caused our mail gateway to suspect that it was a spam email.
Here are some common reasons why this may have happened:
Links which look like phishing links
A common tactic of spammers is to send an email with links which look as though they are going to take the reader to one website, but when clicked actually go somewhere else. As such, if you have a hyperlink in your email where the link text is a domain but does not match up with the link address, the mail filter is likely to suspect foul play.
Invalid or missing SPF records
SPF records are a special type of DNS record which identify the mail servers which are authorised to send mail on behalf of a domain. Large mail service providers such as gmail and hotmail increasingly take note of these and, when a message is received, check to make sure that the mail was sent from a server which is authorised to send emails on behalf of the domain. If you are using a domain which is resolving from the DNS configured in your cPanel or Plesk account, your domain should already have a valid SPF record, but if you are using an external DNS provider you should contact our support team to check that your SPF record is set up correctly.
Spam trigger words or phrases
It could be that the content of your message, or the subject, happens to be using keywords which are commonly seen in spam emails. Some examples of these are:
- Free Offer
- WORDS OR PHRASES ALL IN CAPITALS (particularly in the subject)
- Lots of exclamation marks!!!
- Generic salutations, such as ‘Dear Customer’
- Banking terms such as Statement, Invoice
- Phrases encouraging users to sign in, for example ‘Sign in’, ‘Log in’, ‘authenticate’
Obviously some of the above are perfectly legitimate, but together they may contribute to the ‘SPAM score’ of an email which increases the chances of your mail being misidentified.
Attachments and images
Some spammers attempt to hide contents from spam filters by using images instead of text, and some phishing emails include attachments which they are aiming to trick recipients into opening. As such, emails with low ‘text to image ratios’, i.e. just a small amount of text alongside one or more images or attachments, can sometimes attract a ‘spam score’.
No Subject / special characters / strange spacing
Emails without a subject at all are unusual, and as such likely to be viewed with suspicion. Similarly another trick used by spammers is to try to hide the content of messages by using unusual character sets or S P A C I N G in text, to try to hide the content of the message from spam filters. As such try to stick to standard characters and formatting where possible.
None of the above applies to my mail!
These are just a small sample of some of the more common reasons why a mail has been identified as spam and blocked. If you would like some further insight on a why a particular email was blocked, please contact our support team by raising a ticket through your client area of the website, and provide the from address, to address and rough time at which the email was sent (note the logs of the mail filter are only retained for a couple of days, so it will need to be ‘recent’) and we will investigate for you.
Please note that our spam filtering mail gateway appliance uses some proprietary rules to identify spam, and these are kept secret from everyone - including ourselves - so as to prevent these rules entering the public domain and being ‘reverse engineered’ by spammers. As such we may not always be able to identify the exact cause in the case of each and every email, but we should be able to offer advice on changes which you can make which can help to reduce the chance of your mails being considered to be spam.