Suspicious message warnings come from Heuristic tab of settings (Internet Mail provider).
Open the provider and check your Heuristic settings.
Which is the reason given in the message?
No… LEFT click the avast blue icon on system tray.
Click on buttom DETAILS.
At left check the Internet Mail provider and at right click on CUSTOMIZE buttom.
Then you’ll see the settings.
Go to the Heuristic tab of settings and configure them.
More info about the options on help files.
If you don’t know how to manage, disabe Heuristics…
White spaces are often used in either subject or attachments to try and disguise the true content. There really shouldn’t be a legitimate reason to do it so it is flagged as suspicious, the one thing about it is at least it wasn’t detected as a virus.
If you don’t recognise who it came form and can’t confirm who it came from (contact them by another means) then the easiest and safest thing to do is delete it.
Open the Internet Mail on-access interface and click the Customize button, Heuristics to see what is checked. See the avast! help file, Resident Protection, Internet Mail, Heuristic Page.
Check whitespaces sequence. Some viruses use a trick: behind one extension of the infected file name a large number of spaces (or other nondisplayable, "white" characters) is appended, followed by a second, real extension that is dangerous. The user does not see the second extension (it is several lines below or does not fit into the window where names are displayed). Heuristic analysis can uncover this trick and warn the user. Default permitted sequence length is five. Thus, if there are more than five white characters, a warning message will be displayed.
Around Apr of this yr "RejZor" posted a "Proactive
Protection Guide", which included a "Internet Mail Proactive
protection" section near the end. You can view this at :
http://forum.avast.com/index.php?topic=20412.0 .