Until about 2006, Mail was catastrophically broken. There were implementation decisions, not "bugs", that were both generally stupid (like deleting all remote data from a server when removing a profile) and horridly abusive of the IMAP protocol.
It's gotten much better in the last couple of years, to the point where I now find it usable (I'm a mail client dev myself, and have hacked on mail server software like Dovecot). It still has some stupidity, but at this point I'd probably call it the best of the Big Three (Outlook, Mail.app, Thunderbird) for IMAP. When I say that, I'm talking about both the interface, and minimizing the abuses of the protocol that manifest as user-noticeable performance degradation when the user does something perfectly acceptable.
They've made a conscious effort, with their devs becoming active in the mail community.
This is good to hear, but if it was so catastrophically broken, how come I have managed to use it to pick up and send email using multiple email accounts for many, many years.
If don't mind me asking as you are allowed to say, which mail client do you develop on?
Why Apple Mail Sucks.
It's slow.
Relative to what? This could be determined by so many possible factors and will probably vary from user to user. I have around 4000 message across all inboxes (not a big sorter) and it the performance is fine. Slow compared to what?
You cannot type "Jo..." and have it go to the first message that is written by Joe Smith or John Doe.
Yes you can, when sorted by subject.
The search is not so good.
In what way? Everything is indexed and fast. You can type things like to: from: and subject: to narrow your results
Copy addresses (right click) gives you the address, not the name and address.
If you paste it into a to field, CC field or BCC field you get the name and address.
There is no notification feature (e.g. request notification that recipient has read this.
True, but that doesn't mean it sucks. This is a missing feature.
You cannot stop a message from sending without quitting the program.
Yes you can, you can bring up the activity monitor and click stop.
It does not automatically create hyperlinks from urls.
But they will be hyperlinks when you view it in drafts and sent.
Again, slow compared to what?
There's probably more...reasons it sucks.
And you've barely named one.
For those criticising Mail, here's a “feature” in Windows Live Mail:
[1] If the Mail body hasn't loaded and you click on the subject (in the sidebar) then nothing happens.
[2] Once the message body is loaded, nothing happens.
The only way to see the body is to click on the message again.
Mail has handled this far better since forever. The body always shows up as soon as it has loaded.