hi,
i received a message from Avast : [avast! heuristique - AVERTISSEMENT] Extension(s) suspecte(s) des pièces jointes
- PC Portables - Boutique HP France.mht
but i’m sure of this message, is it possible to authorize the reception of this mail.
Thx
More info please. Was the email from someone you know and trust? If not, you may want to think twice before opening. 
What avast version do you have avast! free/Pro/AIS ?
This appears to be an alert on an email which has a .mht file attachment that avast considers suspicious.
[avast! heuristique - AVERTISSEMENT] Extension(s) suspecte(s) des pièces jointes * PC Portables - Boutique HP France.mht
Was all of this in the email Subject/Title as avast would modify the title as a warning. The .mht file is an archive of a web page with embedded images and or elements, so actually opening the .mht attachment could trigger scripts embedded in the page.
If you are confident of the source and accept the risk of accepting you can lower the Heuristic settings in the Mail Shield, Expert Settings, Mail heuristics and uncheck the ‘Attachment check’ option. This however, would apply to all attachments and all email not just from this source.
You could also try - Mail Shield, Expert Settings, Actions, Suspicious tab, Set the first action to Ask and secondary action to No Action. Obviously this carries risk as it too would apply to all email.
You would then need have the sender resend the email and attachment.
I just had this same warning too:
[avast! heuristic - WARNING]
Suspicious extension(s) of attachment
- Redesigning the Windows Logo.mht
It’s a web page file container from Opera I emailed to myself from another location.
Then the latter part of my last post still applies as .mht attachment files can present an immediate risk when opened as everything that was embedded in that web page, scripts, etc. are present and they aren’t commonly used in emails.
You can do as suggested and uncheck that option, if you accept the potential risk (I wouldn’t); so you are left with the other option if you don’t want to uncheck this option, set the Mail Shield, Expert Settings, Actions, first Action to Ask and second action to No Action, for all of the tabs. Then you have to decide what action to take.
Thanks. Would zipping up the mht file first prevent avast! from flagging the attachment?
Only if you use a password protected zip file.
You’re welcome.
I don’t know if zipping, even with password protection would work as password protection stops the contents from being extracted to be scanned. But I believe you can still see the content files, so if the avast check is attachments, I wonder if it would apply to the file types contained in the password protected zip attachment.
Me, I’m all for the simple life and not having to zip and password protect to avoid a scan option and just set my mail shield to Ask as the first action and I decide. Not to mention, you have no control over what email you receive, so can’t zip and password protect attachments in those emails.
What if I just changed the file extension of an mht file to something like txt, would that bypass the heuristic scan?
May I ask, what you want to achieve…??
Just to be able to send those types of files to myself. Otherwise I can just copy and paste a URL.
See: Reply #6 then or set the mail shield to “Ask”, as Dave suggested. 
Done. Thanks for the info
You’re welcome.