If you are using Windows or OSX, try this add-on:

https://addons.mozilla.org/en-us/thunderbird/addon/theme-font-size-changer/

Have tried and failed to download the add-on. Am utterly frustrated that there is not easy way to do such a simple thing as increasing the font size so that the site is readable. Gerry

How to install add-ons: http://xenos-email-notes.simplesite.com/416814616

In summary:

1. Go to Tools|Add-ons in Thunderbird;
2. Switch to its Extensions tab;
3. Type Theme Font & Size Changer into the search box;
4. Click its magnifying glass;
5. Select the required add-on from the list (assuming multiple add-ons are offered);
6. Click its Install button.

Thank you for sorting out a problem. Gerry

Wish this worked for the same problem in Windows 10. Thanks for the help with Tbird.

I'm using TBird Beta 54.0b3 32bit with Theme Font & Size Changer installed but it doesn.t change my font size. If I change the size of the font in the TF&Size Changer it keeps making the number keep going higher with the dialog box getting larger. It only changes template not the font in the message. In my attached image I would like to make 2017 & Happy Father's Day larger than Huge gives me. A recent change deleted making the font larger & added the scale of Tiny to Huge. Would lke to know if I can make the 2017 & Hap....... larger.Thanks much, c somers

You really should start a new question. The original question was about the menus, lists and the answer was about an add-on.

To adjust the size of text in messages you just use Thunderbird's own internal controls.

http://xenos-email-notes.simplesite.com/417754775

If you are not satisfied with the range of sizes offered, this add-on:

https://codefisher.org/projects/extra_format_buttons/

may be useful. I use it to repair messages damaged by Outlook.

Be aware that in following the previous two suggestions you may find they counteract each other. Setting fonts and sizes to suit you stops Thunderbird from being wysiwyg, so you may not get a fair idea of what your greeting will look like for Dad.

In general email is NOT wysiwyg. I would add the text to the picture, using a graphics editor (e.g. Paint, Gimp), and then send the altered image. This way you have total control of the text vs image size, something that cannot be guaranteed using email or web technologies.

And why are you using a beta version? Beta versions are for experienced users who are looking for faults and bugs. You appear to have misunderstood the purpose and effect of the Theme Font & Size Changer add-on.

Hi Zenos. When I signed into TBird this morning to try the links you sent, I find that all my TBird .data is gone. All that comes up is the Home tab asking me to create a new account & I can't get any of my old files. Can you help me out on this? Thanks much, charlie S.

I tried to respond over the weekend but it told me I wasn't connected so maybe this won't go thru either. I read in one of the responses that he had lost some of his TBird info & it was blamed on CCleaner which I'd used the day I lost all of TBird stuff. I read the fix for getting back all the data but it looks too hard for me to follow. I'm now undecided if I'll try TBird again.

I think I downloaded a new revision & got onto Beta. Thanks again, c.somers