The last couple of days I have had users attempting to send emails to particular domains that are being filtered by messagelabs.
We are regularly reciving immediate bounces with the following error code:
cluster4.us.messagelabs.com #5.0.0 smtp; 553-Message filtered. Refer to the Troubleshooting page at 553-http://www.symanteccloud.com/troubleshooting for more 553 information. (#5.7.1)
One of the techs here decided to remove our email signatuire and attempt to send again. To our amazement it appeared to send.
Further investigation found that the removal of a specific hyperlink on an image displayed in the signature was the cause of the problem, in fact we had other images in the same signature that had links to them (that were not removed) and the email went through still.
There is something specific to this particular hyperlink that has caused the issue but I am not sure what the problem is.
Is there some sort of filter test taht I can use against the messagelabs filters to understand exactly why our signature is causing the filtering of the message?