My reply settings changed recently, but I didn't set it

[cyberzork]

Until very recently, if I replied to an email sent to B while I am working in the A inbox, the message will by default come from the B account. Now, in the last few days, it automatically comes from the A account

What about if you reply to that sender in “All Inboxes” and not directly in that account Inbox ?.

As doing that works for me correctly using the latest eM Client V10.4.4209 for PC & Mac.

See this thread post below from @Olivia_Rust which should explain the problem you are having.

From email address always uses current account

Hi Daren, there has been a slight behavior change to this feature. Specifically, in the account’s Inbox, we prioritize the mail account’s address. However, in All Inboxes, the behavior should remain the same as before. Can you try to see if the behavior is back to your preferred one in the All Iboxes folder? If not, please reach out to our support team. If you have active VIP Support you can create a ticket in our Support center: https://support.emclient.com - just make sure to login with the…