Sounds like those messages are in Plain Text and not HTML.

Plain text, as the name indicates, does not allow formatting or inserting images.

Airmail said

Sounds like those messages are in Plain Text and not HTML. Plain text, as the name indicates, does not allow formatting or inserting images.

No. If I receive an e-mail that has formatting (bold, colors etc) and pictures and I try to reply all the formatting and pictures are stripped out and text forced to wrap at I think 80 characters.

What happens if you hold the shift key down when clicking reply to one of these messages?

jrowan said

I can't remember when it started but some of my replies won't let me use bolding, formatting or insert images. It's only some replies, other replies allow formatting, images, links etc. I've gone through Account Settings, Composition and options but can't find why some only allow text.

I wasn't aware of the shift+reply method. It does allow me to have a formatted reply and insert images. Is this some new feature?

No, it switches from plain text to HTML or HTML to plain text. It was to prove my point that for some reason your replies to the problem messages were in plain text. Do you have these senders in your address book tagged as preferring text vs HTML? The shift click works on any action that opens a write window.

Airmail said

No, it switches from plain text to HTML or HTML to plain text. It was to prove my point that for some reason your replies to the problem messages were in plain text. Do you have these senders in your address book tagged as preferring text vs HTML? The shift click works on any action that opens a write window.

The entry in the address book had unknown as preferred format. I changed to HTML, then tried replying, it opened reply window as text, not html.

I will ask one of the mods if they have an idea why it is trying to use text. I am not sure where to look now.

Try looking in Tools menu (alt+T) > options > General > Send options.

In the send options dialog click the P{lain text domains and delete anything that is in there. Do the same for HTML. In about 99.9% of cases both those items will be empty these days as basically everyone does HTML mail.

It is also possible that the entry in the address book is duplicated, so your getting a false response from looking it up. Check ALL your address books for that address. ( I have some addresses in a Gmail address books, the personal address book and a Mozilla one as over the years they have been duplicated as I have migrated around the place and synchronized address books that were previously stand alone.

Have you now or previously installed the addon Enigmail. It turns off HTML composition, but that is for all mail. Not only some. The issue might be masked by the mail your replying to containing elements that do not convert to text so HTML is retained. Thunderbird is supposed to do things like that. Stick with HTML when not doing so would loose content. Clicking write and getting plain text would be a clue this is the issue.

Tools menu (Alt+T) > Account settings > compositions and addressing. Compose in HTML is the first thing in the panel

I looked at Tools >Options >General ->Composition >Send Options, there is nothing in Plain Text Domains. The HTML Domains has Send message in HTML anyway. I had duplicate entries in the address book in both Personal and Collected addresses. I also had a group with third of the same address, removed all but one but when replying it still defaults to text only.

I don't think it's related but I have multiple accounts set up. Some times when I send an e-mail it doesn't get written to the sent folder, it is sent but is not saved in any folder.