Let me reply to your points individually:
With regards to single point of attack, the last 30 days of messages could be read, not all messages. I could keep multiple accounts so only some messages are compromised in this wurst case scenario.
If a single point of failure is an worry i am happy to add fallback urls to other hosts. I'll make a note.
There is definitely a need for this central setup though: 1) almost no average user knows their smtp details or knows where to find them. 2) I don't want loads of complaints of non functional smtp configurations due to firewalls, typos, edge cases. It reflects badly on me and the program when it is not working. The current setup works for everyone. 3) entering a bunch of configuration details is not a pleasant experience and is a significant barrier to using the program. I have looked at thinderbirds auto configuration documentation and perhaps mail settings are stored in the registry but implementing this might push auto hotkey too far.
And just as a FYI when delivering your regular unencrypted email, it goes through a bunch of servers that can read it.
That said i agree the setup is not ideal, I'm trying to find a balance between the various factors.
I could add the functionality you asked for and make it optional, and I will be supporting two solutions, add complexity to the program, and any time spent on the central setup will not benefit the other setup and vice versa. Sounds like the worst of both worlds.
I'll think about it.