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thunderbird email suddenly giving error "Assembling message" then "sending of the message failed"

  • 3 replies
  • 1 has this problem
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  • Last reply by jeff150

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I sent several emails this morning. Then I updated some message filters. Then the filtering process seemed to take off and not respond. I ended the thunderbird task and since then I have not been able to send any emails. thunderbird email suddenly error "Assembling message" then "sending of the message failed".

I found a possible reason but do not know how to remove any temp files or reset something to help this. On bugzilla https://bugzilla.mozilla.org/show_bug.cgi?id=1222992

Same error message "Sending of message failed", but different cause. TB 78.7.0, WIN 10

TB creates temporary files in user's TMP folder with a naming pattern like nsmail-????.eml And ???? is limited to 9999. After that - user cannot send messages or save drafts.

I am running Windows 10 home, thunderbird 78.8.0 (64-bit)

I sent several emails this morning. Then I updated some message filters. Then the filtering process seemed to take off and not respond. I ended the thunderbird task and since then I have not been able to send any emails. thunderbird email suddenly error "Assembling message" then "sending of the message failed". I found a possible reason but do not know how to remove any temp files or reset something to help this. On bugzilla https://bugzilla.mozilla.org/show_bug.cgi?id=1222992 Same error message "Sending of message failed", but different cause. TB 78.7.0, WIN 10 TB creates temporary files in user's TMP folder with a naming pattern like nsmail-????.eml And ???? is limited to 9999. After that - user cannot send messages or save drafts. I am running Windows 10 home, thunderbird 78.8.0 (64-bit)

Modified by LisaFern

Chosen solution

all good, addressed by fix in Bugzilla https://bugzilla.mozilla.org/show_bug.cgi?id=673703 in the C:\Users\user\AppData\Local\Temp there were 9999 nsemail* files, some limitation in TB.


"Sending email fails if the limit of 10000 temp files is reached. I.e. there exists nsmail-9999.tmp in C:\Documents and Settings\User\Local Settings\Temp.

In fact TB is limited to 10000 temp files and cannot create a new temp file beyond nsmail-9999.tmp. TB fails without appropriate error message. It also does not remove its temp files, at it should."

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I also have access to this same email on other computers with no problems. It seems it is only the one where I had the filters that is being affected. I have since disabled all filters. What is the process/service/file I need to change to fix things so I can send emails? I have also rebooted, reinstalled thunderbird, added one filter to see if it would kickstart some change but nothing is helping.

Modified by LisaFern

more options

Chosen Solution

all good, addressed by fix in Bugzilla https://bugzilla.mozilla.org/show_bug.cgi?id=673703 in the C:\Users\user\AppData\Local\Temp there were 9999 nsemail* files, some limitation in TB.


"Sending email fails if the limit of 10000 temp files is reached. I.e. there exists nsmail-9999.tmp in C:\Documents and Settings\User\Local Settings\Temp.

In fact TB is limited to 10000 temp files and cannot create a new temp file beyond nsmail-9999.tmp. TB fails without appropriate error message. It also does not remove its temp files, at it should."

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I had the same this morning (on Ubuntu Linux). It turned out that the disk with /tmp was mounted read-only, so Thunderbird couldn't open any new temporary files. So I suggest tracing the Thunderbird process to see what files it's trying to open (sorry, I have no idea how to do that on Windows). This certainly seems in line with the other (very old) suggestion that it's to do with opening temporary files, but probably with a different underlying cause.