I couldn't see my screenshots added by @rick_clark, so I'm adding them myself. This is more than a feature request. The current UI is so crowded that letters with tails on one line overlap with accents on characters in the next. It's bad UI design that needs fixing.

Yes please, this function is something we are really missing. Would be great to add this to eM Client!

Jumping back in this thread to point out another reason why the current line spacing is problematic: When you add an emoji, it changes the line spacing for that line only. Emojis are a fact of life in email, their use shouldn't cause layout issues.

Hi there - just adding to the trail...I recently joined the eM Client community and enjoying overall the software on my Windows PC....gladly replacing Outlook which as limiting my mailbox size to 50GB.....The Line Spacing in composing emails is indeed much needed (all other formatting options work great but this is really lacking...not sure why). Thanks

I agree with that. There urgently needs to be a way to adjust the line spacing / formatting. Nowadays you copy texts from Word, Chatgpt etc, where there is often unwanted spacing. You don't always want to paste this directly as text, as links are then also lost.

Please be sure to adapt and include this formatting option.

Please add Paragraph function and Table function as outlook, this will be very useful when working on EM Client

Line Spacing in composing E-Mails is necessary.
Adaption of other formatting options to Windows Standard (e.g. get a drop-down menu when right-clicking to quickly chose bold) would be really helpful.
Formatting is no fun in eM Client (saying so on the first day using eM Client, after I got swiched from Outlook to eM Client in the office).

I would like to add that not only in composing but also in the email viewer pane a higher default line height would be beneficial. As mentioned by @robiomailsoftware the line height is way too narrow, this makes reading long emails cumbersome. Look at it like a book, no book looks this way.
In that sense it susprised me that we can change the line height in the list view but not in the email preview pane. In general more customization opens for this pane would be great. Thanks!