Is it possible to configure a reply-to address; i.e. an e-mail that is different from my account on the imap server?
Yes it is. It is called Alias. Go to Preferences>Accounts>Aliases.
Is it true that the alias should be in the same domain?
I tried to use another domain because I have new email address, but when I select that address when I reply to a message the screen just refreshes.
The solution checked above seems to be incorrect.
Using Mailspring’s alias feature causes my mail provider (Zoho) to reject the outgoing email, unless SMTP relaying is configured with the provider in advance.
By contrast, a custom reply-to address is supported in apps like Thunderbird, Mailbird, and maybe Outlook. In these apps, a user-specified reply-to address is appended to the outgoing email, which causes the respondent’s reply (if any) to be sent to the “reply-to” address rather than to the “from” address.
I’d be curious to know if development plans include adding custom reply-to address to Mailspring?