When a message is sent to a recipient, the message is shown in the Message List not with the name of the sender but with an arrow and the name of the recipient.
Currently, this arrow is ASCII-art "-->". This is stone-age technology which does not fit a modern mail tool like Claws.

Claws is Gtk based, and Gtk supports a vast collection of Unicode glyphs representing arrows. In particular glyphs U+279C "➜" and U+21AA "↪" are good candidates.

Having more candidates leads to an implementation where the user can choose what glyph she wants. This is no problem, especially since this also deals with the (imaginary?) case where the user has a system that does not support the desired glyphs.

There's one final question, though: Should the Unicode arrow glyph be made default, modernizing the Claws UI while still allowing the user to change it back to "-->" or something else, or should the stone-age "-->" be kept and leave it up to the individual user to modernize it.

When there's consensus about the approach I'm willing to provide the necessary patches.