re: but when I copied and pasted an online address, it was underlined

by 'online address' i presume you are referring to webpage address as shown in the top address bar of the browser so you know what page you are looking at: eg: https://www.mozilla.org/en-US/thunderbird/all.html

If you use 'Insert' > 'Link' method then the link is added and underlined. Simple Copy/paste or hand typed Links directly placed in the composer are not underlined in the composer, but they become auto underlined after sending or if you save as Draft. If you save as Draft and then choose to edit the draft, you would see the link underlined in the composing area.

However, if you have done a simple copy paste, but copied a piece of text from a webpage which was an underlined link, not copied from the address bar, then you will have copied some of the formatting as well. If I do this and then backspace and then type, that copied over hidden formatting will still be used and look like part of the link. Although if I press space the underline does not continue, but then it does depend upon the exact moves you are making and the copied text may have included a blank space with hidden formatting. If this sounds like your situation - copying text that says it is a link try going to the link and then copy pasting the info from the address bar and not the text link.

You can see what is going on with the fomatting. save as Draft, then go to Draft folder, select email and click on 'Other Actions' > View Source.

I'm using version 31.2.0 What version are you using.

Thanks for your remarks. I am using v31.2.0 just as you are. I was so used to working with Outlook 2003 but it began acting up after MS discontinued anything that pertained to that version and since I couldn't afford an upgrade, my ISP carrier said that he uses Thunderbird and he suggested that I use it and so I am. It appears to be a good program but the font usage is limited as I had always used Word for Windows to compose messages with and then everything worked just fine. Can't manage to do the same with Thunderbird, it has a mind of its' own.

Hi once again. I was just going over another reply and it was most helpful and that is simply after pasting the website or such, the copy and paste a few words of my original text and then simply continue typing more of the message and then simply go back and delete the few words I had pasted of the original text. That seems so easy and it works nicely. Then I don't have the underlining continuing with my new text.

Hope that this idea works for you as well.

RHartsook