The existing default font appears to be New Times Roman 8pt. Please provide Arial or Tahoma fonts in 10, 11 and 12 pt.

I too have low vision and cannot read the small font.

Larger characters in the mails and different spacing for the paragraphes.

Yes, I think it's necessary to consider the needs of persons with relative disabilities, including the decline in vision that comes with aging.

Yay!!!!

It will be very useful if Protonmail allows user to set the default font type and font size.

The more you use the technologies, the more you become dumber.
You can simply CTRL + zoom (with the mouse scroller) or +/- on your keyboard, or use the zoom in your browser...

"do you pay by the font size" lol

Same on Android; UI size is an issue, but I can hardly read some emails that arrive because the font size is too small.

I use the mobile app exclusively and I agree that some larger font options would be extremely appreciated!

For those interested: you can change the default email font-size by copy/pasting the following css-code to Settings > Appearance > Custom Theme:

#conversation-view .message .frame {
font-size: 20px;
}

Hit the save-button and it should work! You can change the size to your wishes.

Geezer here: those of us over 40 generally are becoming progressively nearsighted, unfortunately.
Lots of "reader" eyeglasses being sold everywhere, proving the demographic need.
It would help...

I agree, having the option to increase the font size when reading e-mails (Small, Regular, Large) would be extremely appreciated. I read and write tiny font all the time but I find the tininess of the default ProtonMail font size when reading e-mails to be an eye-strain.

One key thing is adding inline images, properly. If I add an inline image I just took with my phone, it does an ENORMOUS (visually, and size-wise) attachment that can't be resized. So, I usually have to take a manual step by opening the pictures I want to include, in Photoshop, to make them smaller, before adding them to a protonmail message.

EMOTICONS!?!? WE DON"T NEED NO STINKIN' EMOTICONS!!! (Paraphrase - Treasure of the Sierra Madre 1948)

And I am SO completely kidding!

You are spot-on in fact. It is nearly 2018. Emoticons have been in use in emails since nearly the beginning. Now we have graphic emoticons, or more accurately, emoji, that have been standardized and incorporated into the Unicode consortium's Unicode Standard beginning with version 6 which included some 80 emoji and increased with each subsequent update of the standard to present with version 10 which now features more than 200 emoji!

I cannot speak to what, if any, risk the sender or receiver of an email containing an emoji might face, but I intuit that it is negligible, else their use would have fallen out of favor long ago.

So YES, DEFINITELY! Emoji ought to be made available to ProtonMail customers AS AN OPTION, just as plain text and HTML enhanced text are offered as options now.

And with that segue, let's briefly discuss the HTML text editor currently in use for customers that wish to use it.

I have just one thing to say: TinyMCE. Predominantly Open Source, very stable and almost an industry standard which some proprietary WYSIWYG text editor are jumping through hoops to compete with.

I am certain there is some rationale as to why TinyMCE was not implemented as the WYSIWYG text editor for ProtonMail from the beginning, but while some would find that interesting, it is really neither here nor there when discussing improving ProtonMail's text editing capabilities.

Yup, we really need a button to switch to "plain text only mode".

This is free secure service. Pick your battles, friends.

Planned..........since February 04,2016. That was 11/2 years ago .......

Definitely the Text Editor in the web interface needs some love :-)
It's almost the same since the first release of ProtonMail, but now it's time to improve it.

All of you must have perfect eyesight. I have low vision, and I would really REALLY appreciate if you could have an option of larger font or bold print. Even when I change the font size on my phone, it does not affect the font size on your app. Please please! Thank you. Otherwise really love your service.