The default mail client on my MyTouch4G dings. A lot. It makes me friggin' batty with all of the dinging that it does. Once it gets a message, it persists in telling me about it until I do something. It will do this all night long if I don't remember to put the phone on silent. In addition, the default client periodically deletes all 7 of my e-mail accounts. These things made me a very unhappy camper and set me to looking for a replacement.
Everything I read said that K-9 mail was the perfect solution to my problem, so I tried it, at the very low price of FREE. After the great reviews, I was willing to pay for the thing, so the free price was a bonus. I installed K-9 and set up my 7 accounts and hoped that I was on the road to e-mail nirvana. Unfortunately, nirvana remains a good distance away.
Things that work:
* I was able to hide the combined mailbox. I like segregating my email accounts, so see no need for a combined folder to clutter my view. Some people may want one. Giving people the option is a good thing.
* It is quicker than the default client, at least with my IMAP account. Maybe I finally got the account set up correctly, but it works a lot better in K-9 than an in any other client.
Things that don't work, at least for me:
* K-9 can't deal with attachments to messages sent from Outlook unless the message was sent in plain text format. I am not able to ask my clients and opposing counsel to re-send things in plain text just so that I can read their attachments. This one failure completely ruins K-9 for me. However, the developers MAY be addressing this in their next major revision.
* Dogs can't count. K-9 does a good job of notifying me of new mail, but always has the wrong number of messages in the notification message. This is a minor niggle, but it is something that they should look at.
* No widgets. I got really used to the default mail client having a widget for each of my two main accounts with a little number on top of each one telling me how many messages are unread in each one. K-9 lets you put an icon for each account on your phone, but it doesn't do anything but take you directly to that account.
* It just doesn't feel right. The default mail client felt natural to use. K-9 feels like a kludge.
When I discovered that K-9 did not support attachments, I went back to the default mail client for a while, but then realized that I only needed that for attachments, so am using K-9 primarily, with the default client set up to access, but not automatically poll, accounts so that I can get messages with attachments and download them as needed. Like I said, using K-9 is a kludge. This whole e-mail problem just makes Android look bad.
UPDATE: When I finished writing my review, Amazon displayed ads for some other products that I might like. One was Maildroid, which intrigued me. I read some reviews and decided to give it a try. It is a great product and I have now paid the $18 for the Pro version (unfortunately, I had to get it from Google, as Amazon does not sell it) and dumped K-9 entirely. Maildroid "feels" right. It took about 30 minutes of tweaking to get it set up exactly how I like it, but that's not bad with 7 email accounts. Bye bye, K-9.