Before you start you need to identify the type of file you have attached. It is not "scanned document" Brother, the maker of my printer offer a number of choices. See https://support.brother.com/g/b/faqend.aspx?c=us_ot&lang=en&prod=mfc8952dw_us&faqid=faq00000046_004

Once you have identified the type of file you can move on to what application opens that type of file. Noting here that the file extension has application to file types only in Windows, not in other operating systems and not in internet documents of which email is one, web pages are another. Hence my comments about some cheap printers below.

Note that many cheap printers have no idea how to attached a document to an email correctly and attach them as text or some for of format flowed binary. Thunderbird will not be able to open them successfully because they are not correctly described. But lets first work out what file format they think they are using.

Hi Matt, Al Scanned Documents are in PDF format & in high Quality very accassionly,I wiil need to add a JPG file Where can I alter the preferences in Thunderbird Thanks Darryl

Sound to me like your AI might be hallucinating. Thunderbird handles PDF files internally. Can you open the attachment from the sent mail folder after it is sent? Or do you get the same error?

Hi Matt,Thank you for your assistance Yes after sending the mails.I can open the attachments ok The problem creates before I send the email I just need to open the attachments,to check & make sure it is the correct attachments thanks Darryl

So no hallucinations then I guess. But if I attach a JPG to an email I am writing, a double click opens it. Attach a PDF and it also opens. In a new tab in Thunderbird. That would indicate there either the formatting of the email you have is wrong (that hallucination) or you have never opened a JPG in Thunderbird. A PDF comes predefined, hence my suggestion that your search on that below

What is showing in settings for helper applications. (search pdf)

Hi Matt,I went into settings,but no application helper

Hi Matt,I went into settings,but no application helper

I told you to search for PDF. It is even shown in the search box of the image I posted. Please do as asked if you want to locate the appropriate settings.

Hi Matt Sorry attached is screen shot

Hi Matt,Apparently I did not supply you with enough information,as I have not heard from you???? Please advise or make a suggestion Thanks Darryl

I tried to write a polite response to this and it got lost in the struggles of open tabs. Essentially your associations are dogs breakfast. It is a wonder anything opens like it should. It is how to fix it that is the issue and I think the only real method is to delete he file in 6your profile folder that stores the information and start again.

SO go to the help menu and select troubleshooting information and then click on the show profile button. It is towards the bottom of the Application Basics" section Close Thunderbird as in shut the program down so it is not running at all. In the windows explorer window hat opened when you opened the profile folder, locate the handlers.jsopn file and rename it oldhandlers.json Restart Thunderbird. Now you should be reverted to a set of new install defaults.

To keep things clean, do not select use this for ever more buttons. Just this once until you are sure your choice for that apparent file type is correct. I am guessing much of shat you are saving is malformed attachments. Hence the plethora of odd mimetype and legacy rubbish that really should not exist in your file at all.

Note this part very well, email uses mimetypes to identify files not file extensions. It is here that many folks, including highly paid computer programmers, drop the ball as their knowledge does not extend past the windows vision of a file extension. The result is malformed email attachments that have no right even being sent out. Some open correctly, others not so much and in some cases only once the attachment is saved as a file so the windows world view is again restored as the only view. If you are at all interested in what these mimetypes are, and there are a lot of them hundreds and hundreds, have a look here https://www.iana.org/assignments/media-types/media-types.xhtml

Matt or Should I address you as a idiot I politely requested Help But your Attitude leaves a lot to be desire(Pathetic) Why with your attitude would even reply to try & help out a person,I cannot understand DO NOT BOTHER REPLYING AS You Are BLOCKED from me even seeing any of your future Responses I will put up with my problems & if needed,change my Email away from Thunderbird Peed off

I tried to be polite, but you have correctly identified my feeling about you and your issue. It is one of your own making. Your desire to not fix it is entirely your choice. Bye now, have a nice life.