@thathipasanna - it depends. Copying and pasting within AquaMail *should* preserve formatting, that's handled by the system.
When accepting shared text from other apps, I strip formatting, that's intentional, but perhaps I should reconsider.
Sharing incoming message text from AquaMail into other apps uses plain text, because there are too many app with bugs in their shared text receiving code.
Finally, copying styled text out of AquaMail's rich text editor is handled by the system.
@fatappel - I'll write it down. If it's because you prefer using a separate .eml handling app, may I know what makes it more attractive?
PS - I'm cautiously looking at tomorrow (Thursday) night (Moscow time, GMT+0400) to release a bug fix update to Google Play.