thunderbird blocking extensions

Without antivirus activated thunderbird is blocking certain extensions, i can't send them at all.

'there is a problem adding the attachment test.wsf(.vbs, .pif) would you like to send this email without the attachment?' yes, cancel.

Other attachments are ok, I've confirmed the smpt server is not blocking mime headers or anything like that.

After much searching, I can't find any other discussion of this problem or any thunderbird functionality that would refuse to try to send certain extensions.

.js, .wsf and .vbs are some of the extensions that cause this while others like .zip go through normally.

What could be causing this?

Does your antivirus software (what are you using?) scan for outgoing mail? (it might not support/allow certain extensions)

Originally Posted by jens Does your antivirus software (what are you using?) scan for outgoing mail? (it might not support/allow certain extensions)

Good question because OP has just stated "Without antivirus activated thunderbird is blocking certain extensions, i can't send them at all." so we do not know if AV has been totally disabled via its control panel or if AV filtering has been disabled inside Thunderbird only (in Thunderbird Security panel).

There are no antivirus addons or extensions in my thunderbird.

The antivirus checkbox in settings is unchecked.

edit: I'm in debian 8, is there a way there could be some other antivirus somewhere that is nowhere visible in thunderbird settings?

I have spent a while looking through thunderbird settings looking for anything that could block extensions and there just isnt anything obvious, which is why I ask what else could block extensions or how could I check for a hidden? antivirus somewhere? Why are there so few intances of this error message?

I only bring the greatest of mysteries to LQ....or when I really dont understand something basic...

Originally Posted by mikudo There are no antivirus addons or extensions in my thunderbird.

I didn't speak about any addon/extension but about your possible usual AV

Originally Posted by mikudo The antivirus checkbox in settings is unchecked.

Do you mean the Thunderbird settings like this? If so, what about the state of your usual AV (outside Thunderbird)?

EDIT: Ok, I've just noticed your edit, according to you, you don't seem to have any particular AV...

Sorry, I misunderstood your first sentence as well.

Whose your email provider?
They can block any file in your attachment as they like.

Google (smtp.gmail.com) has been blocking .vbs, .pif, .wsf, ... in attachments since ages (and .js since 2015). ...

To protect your account, Gmail doesn't allow you to attach certain types of files. Gmail often updates the types of files not allowed to keep up with harmful software that is constantly changing. Some examples include: .ADE, .ADP, .APK, .BAT, .CHM, .CMD, .COM, .CPL, .DLL, .DMG, .EXE, .HTA, .INS, .ISP, .JAR, .JS, .JSE, .LIB, .LNK, .MDE, .MSC, .MSI, .MSP, .MST, .NSH .PIF, .SCR, .SCT, .SHB, .SYS, .VB, .VBE, .VBS, .VXD, .WSC, .WSF, .WSH, .CAB

https://support.google.com/mail/answer/6590?hl=en

Actually this is a test environment I made myself.

The postfix server that catches the smtp has blank amavisd.conf and does no mime header checks in main.cf, it relays to another postfix server that does have amavis installed but which should treat .wsf as a banned attachment, sending notifications etc.

But the behavior I see is that all other attachments go through at least so far but for .vbs, .wsf and two others, thunderbird itself says this attachment isnt allowed, continue without it or cancel.

Because testing things like this is the purpose of this environment, this throws off my whole test.

Thanks for considering this odd issue.

Originally Posted by mikudo Actually this is a test environment I made myself.

Honestly, you should have mentioned this in your first post.

I'll try to duplicate this and post an update plus fix (should be easy).

Sorry but thanks! I try to bring only top quality mysteries to LQ.

Originally Posted by mikudo Sorry but thanks! I try to bring only top quality mysteries to LQ.

Making your mysterie even bigger, it just works for me ... :/
I'll try adding weird options, hoping atleast somthing fails.

I can't duplicate that here, either.

Do you get the error when attaching the file, or after hitting Send?

Are you using IMAP? What are the rules on the IMAP server?

Pop, no security, no authentication method, we are really just testing scanning and notifications so none of that stuff is significant here.

The popup error occurs when I press send. 1-2 seconds after I press send I get:

"A problem occurred when attaching the file test.vbs. Would you like to continue to send the mail without this file?" cancel, continue.

And ive tested about 20 extensions, only vbs, wsf, pif and another odd one have this problem.

The smtp server this tbird connects to then relays to a server where amavis should block by extension, and .vbs and .js are in the same banned line. I dont know how the relay server could directly block at the client or why even in that case the two filetypes would be treated differently.

tbird 52.8 64bit