Do it really attach something or is it just attaching itself to the server? If it take long time the connection will time out. Thats no problem. Even your own isp can put your internet-connection on sleep. Unless there is some net-activity.

Thank you for your response. I have not had an email to reply to that has taken me a long time to compose a reply or since. I tried sending myself an email then take a long time replying as a test to try to be able to provide more information but I couldn't get it to misbehave. I usually know it will want to attach something because a green bar shows along the bottom Right hand end. Next time I see something like this I will try forcing my isp into activity by sending a different email then try to send the "stuck" one. Will also try to produce some screen dumps.

I tried forwarding a mail as attachment, it took a four -five seconds with a message "connecting..... " and blue bar working. It was absolutely the same if I replied with mail inline. blue bar working.

Run a virus-check with different programs just to make sure nothing isn't hooked up for a ride to another pc.

OK will have a go -- might take me a few days. I first experienced this several years ago when I had an XP machine. I used the backup facility to move everything to my new machine to maintain things I have forgotten. I currently use McAfee live safe

do you use any signature-attachment like a vCard? Check if so and that the attachment is as it should be.

My email accounts are set up correctly

I did a full virus scan with Kapersky this afternoon -- did not find any virus's Now just need to wait until an email reply "decides" to behave oddly again.

At last, I have an example I started to reply to an email then looked in another email for confirmation about what I was trying to say clicked send then got the "attaching" message I know my ISP has not gone to sleep. while this email is in this state, I have received some emails. Also after writing this and attaching the file below, I sent myself an email to one of my other email accounts on a tablet -- have just heard the ping. My original email is still in the "attaching" state. My "get out" when this arises it to copy what I have written. Close my "outgoing" email then initiate a new reply and paste my message - sending the new email works perfectly.

When I click close email via the x in the top right of the window I got the message below

What happens if you respond to the same mail. just change the to address to yourself. If there is a attachment in the original post then it won't be in the copied alternative. View source in that email and see if there is an attachment?

OK Will try that next time. Same I didn't keep it open

Have you deleted the email you replied to? If not view that source. Just the way he/she finish it could apply there is music added.

I still have the original emails with all their history. No music -- the first received email has a screen dump of some text. No attachments but has a link to a youtube video about a fancy optical scanner. Will pay more attention to the extra content when it happens again

I think I know what is causing the problem The email goes into attaching state. The email I replied to today "hung". So I followed your recommendation and re addressed it to myself. It still "hung" until I deleted the two screen dumps contained in the source file. There was no evidence of anything in the email sent to myself (after deleting the screen dumps). I had also copied my reply and pasted it in a new reply to the original email which posted without any problem while the other was still in the "hang" state. At least I know how to "cheat" the problem

McAfee will be the problem. Turn off the mail attachment scanner and watch the problem vanish. (note that screen dumps are files in your temp folder than must be incorporated into the mail before it is sent.) McAfee has been a pig for years now with regard to Thunderbird.see https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#McAfee

Thank you Will give this a try

The last posted suggestion didn't work. Had to copy my reply. Close the reply re open email paste the reply -- noticed a screen dump from the original was blank Which should be OK I have to assume the reader rembers what they wrote