''[Locked as a duplicate of https://support.mozilla.org/en-US/questions/1349640. Please follow up there, thanks.]'' Please be patient and digest my problem. I'm a 76 year-old, tech/Mozilla-friendly, male who has enjoyed Thunderbird, daily and for hours, for years on my now old laptop. My son installed that Thunderbird for me about 10 years ago and I enjoyed its benefits immensely. Recently I bought a new Chromebook and installed Thunderbird on it but am having problems customising it to my needs and am encountering basic problems e.g. emails are appearing on my screen far too big! CONTROL plus + or - gives me the correct size but I can't make that size permanent. For the last 3 weeks I have being sussing uTube, Google etc in my efforts to get Tb tuition, for which I am only too glad to pay for, without success. Pleae, pl;ease, please help me!