I usually delete all the message of the mailbox to keep my mailbox clean since I receive too many e-mails. Often, when I delete all the messages (even with just 1) from Inbox I get immediately "Loading error", then after a while the client retries automatically to refresh the mailbox so I get "All messages loaded".
Steps to reproduce the problem:
1) use an IMAP IDLE account
2) empty mailbox in AquaMail from the Inbox list (select all, delete)
3) send a new message to the mailbox
4) delete it in AquaMail
Regards,