I use "redirect" in filtering to forward priority messages to my Android phone. Unfortunately, given below:

1) I am composing an email and
2) Claws is receiving emails and
3) Claws is filtering the incoming emails and
4) A filter matches my priority conditions, and redirects the email

Then:

Whatever I am composing stops dead - and a window appears showing the redirect occurring. Only when the redirect is complete can I continue composing my message. If the redirect is an email with a long attachment - in can take several seconds before I can continue.

Since redirects can occur at any time - including several while composing a long email - this can be a frustrating experience.

I haven't looked at the claws code - but if feels like Claws is not multi-threaded for writes/redirects - which is why the compose window waits while writes/redirects are taking place.

My sense is that this enhancement would be a worthwhile investment of the Claws Team's time and energy - and would help Claws become a more efficient and attractive product.