re :like send only text mail Presume you mean 'Plain Text'.

• Right click on mail account in folder Pane and select 'Settings'.
• Select 'Composition & Addressing'
• uncheck 'Compose messages in HTML'

• do this for each account.
• click on 'OK'

Check this is correct in the 'About:config'

• 'Menu icon' > 'Options' > 'Options' > 'Advanced' > 'General' tab
• click on 'Config Editor' button

• In top search type: compose_html
• Look for this lines like this: mail.identity.id1.compose_html

The Value should be 'False'

• If it says true, double click on the line to toggle 'True' to 'False'
• close window - top right x
• click on 'OK'

Make sure you do not have any product like 'CCleaner' performing any scans as they have a habit of removing Thunderbird files such as session data, passwords etc etc. Best to make sure such programs do not have access to any Thunderbird file or folder.

You may also need to check that files such as 'prefs.js' in the profile name folder are not 'read only' as this means whilst your preferences are ok during the session, nothing can be saved and used next time.

How to access Profile name folder:

• http://kb.mozillazine.org/Profile_folder_-_Thunderbird#Finding_your_profile

Make sure Thunderbird is closed before doing anything in the 'profile name' folder. Right click on 'prefs.js' file and select 'Properties' Under 'Attributes' 'Read Only' should not be selected.

Is it possible to switch to just plain text in Thunderbird?

I see that mail gets mixed up, html and plain text, and html parts can not be removed partly as I want to do to keep mail clean without not relevant parts repeating.

I see two separate issues here.

First of all, I share with you a suspicion that settings can and do change in Thunderbird. I think it is mostly related to upgrades/updates, where settings are not transferred completely. Over the years we see a sprinkling of complaints about some feature having changed or vanished. Often it may be finger trouble, or PEBKAC. But every now and then it feels like a setting has changed.

If you're convinced this is happening it may be worth making archive copies of settings files, and then running a file comparison between the most recent archive and the current file when you think an unwanted change has taken place. I'd start with prefs.js, since the majority of your settings are stored in here. Of course, you may also find a great many legitimate changes going on too.

Now, html vs plain text. Your correspondents, or their email clients, will send you plain text, html markup and often both. Many commercial messages are almost entirely html, with the only plain text part being advice to get an up to date email client. YOU cannot control what decisions others make and what tools or techniques they use when writing to you. So a mix of plain text and html is unavoidable.

https://en.wikipedia.org/wiki/MIME

I like to think that Thunderbird is one of the most honest email clients out there. It stores messages as received. It doesn't dick about with them. Attachments remain as they came in, part of the message. Headers remain with the messages. You get to see all the correspondents' email addresses. Etc etc.

So Thunderbird is not going to censor or bowdlerise your messages for you. You choose whether to view the plain text component or the html part, but you can't eliminate either part. With the "Show all body parts" feature you can see all these sets of data.

Toad-Hall has pointed you to the setting for the default composition mode, but it isn't a great deal of help when an html message comes in and Thunderbird replies in kind. I understand that in TB60 the preference may change to the composition mode default for the account rather than the mode of the message being replied to.

I think for your own messages you can either trawl through your Address Book and set each correspondent for "prefers plain text", or go to Tools|Options|Composition|General where you can set automatic conversion of outgoing messages. Note it says "plain text where possible" because if you're replying to or quoting a message that includes markup, then you'll need mark-up to convey this accurately. If you really want to reduce it to plain text then you may need to cut it and use "paste without formatting" to eliminate the markup.

So, Thunderbird is offering you two types of plain text. Real plain text, set by the account settings|composition setting (but this only holds with new messages you write, and doesn't apply to replies, forwards or Edit As New), and then there is "after the fact" plain text, where you actually use the HTML editor, but cleanse or downgrade the text on sending. This second one is what is used to honour the preferences in the Address Book and under Tools|Options.

But I want to repeat this: you cannot control what others send to you, so you simply have to work with a mix of html and plain text. And if you want to edit received messages, to strip out the html component, then Thunderbird is not the right tool for you. That's part of the "honesty" thing I mentioned earlier.

I am looking for yet another mail client then. I have one that fits my wishes, it runs under RISC OS, and is called Messenger Pro. It is also available under linux, but does not seem to be the same. I managed to get it to send mail, but not see received messages yet, probably because I use gmail as a inbetween messure before I switch to my own prefered provider XS4All.nl