Cannot attach document files to email

Open a Command Prompt as Admin. Type or copy and paste the following Bold command and press enter.

DISM /Online /CLEANUP-IMAGE /RestoreHealth after that completes type and press enter

SFC /scannow

These will replace any missing any system files.
If this doesn't fix it then

Try a Clean Boot. If this works, you can keep it this way, or you can add one Startup Item or Service at a time until the behavior returns, than you will know the culprit.

How big is the email a lot of have size limit

Hi, try a clean boot (Google or see Tutorial if unsure how). Do you see the same symptom?

Until today I could attach files to email written in Outlook,

Try using a System Restore point created before this started.


No such problem here. Here's one way to add a file as an attachment in Tbird:


What do you see happen when you drag a file onto 'Write' in Tbird?

Another option: rt click the file, click Send To, click Mail Recipient - or you could put a shortcut to e.g. Tbird in the Send to folder and use that if it's not your default email client or the Mail Recipient is broken.

How are you attempting to add an attachment to Tbird? File, Attach?

And what type of file?

Thanks.

Besides the above, which you need to try to see if you can unpack the enigma, you can try creating a new user account for test purposes only and see if the same happens there. If it doesn't, you know the problem is specific to your user account and general Windows repairs will not help.

Once you have learnt what you can from that you can delete that new account.

User account:

Add Local Account or Microsoft Account in Windows 10

- standard diagnostic procedure.

Clean boot:
- also a standard diagnostic procedure.

By not investigating I do not risk harming my setup or creating new problems.

Assuage your fears by using 3rd party disk imaging regularly and routinely to external storage and having a System Restore point created daily on schedule (tutorial available).