Version:           4.8 (using KDE 4.8.0) 
OS:                Linux

If an incoming email has Reply-To set, like for example:

From: Sender Name <name@example.com>
To: list for announcements <announce_list@example.com>
Reply-To: discussion_list@example.com

trying to reply to the author (from) sets To address to the Reply-To address instead of the author's address, i.e. "discussion_list@example.com" instead of "name@example.com"

Also when trying to use the "reply to all" feature, the sender address is omitted, i.e. the list of addresses does NOT contain "name@example.com"

There is no way to send the answer to the sender and not to Reply-To address except for deleting the prefilled address from the reply and entering the sender's address manually.

Reproducible: Always

Steps to Reproduce:
see above, get an email with Reply-To set

1. hit "r" on it and examine the message being composed
2. hit "a" on it ...
3. hit "shift+A" on it ...

Actual Results:  
1. "To" is set to "Reply-To" address - this is correct
2. "To" is set to "Reply-To" and "To" addresses
3. "To" is set to "Reply-To" address

Expected Results:  
1. the same - "To" is set to reply-to address
2. "To" is set to "Reply-To" and "From" addresses
3. "To" is set to "From" address

While it may arguable if the case 2. should include also the original "To", i.e. using really all concerned addresses and not just a subset (when "Reply-To" serves as a replacement of "To"), the most important thing is that cases 1. and 3. have to differ. The "reply to author" function is chosen explicitly when the reply should go to the sender, overriding the implicit mechanism of chosing the address in standard reply.

Note that this has worked as expected until kmail 4.7.4, it got broken in 4.8.0.

p.s. my case is using this with mailinglist where other headers that I haven't mentioned like "List-Post" may have some influence - if an exact reproducer message is needed, I'll try to refine some