The difficulty transferring data is why I switched to Thunderbird years ago, though I never fully converted my archives. I regret that now, since trying to make sure I have all the old data means installing Incredimail, which is harder to find now that Incredimail has redirected most of the website to a shutdown notice. The versions on Filehorse and OldVersion seem to be infected, but going through the Wayback Machine got me signed files from Incredimail, even though I couldn't get to the download page directly from Incredimail's homepage. Adding the Premium registration number doesn't work anymore, though.
Thunderbird has a how-to Importing from Incredimail page which links to some tools that help convert Incredimail to .eml files. At the time I switched, I had Incredimail XE and the older converters still worked for me on the files I had then.
Incredimail sent me an email notice for the scheduled shutdown, since I did pay for the Premium Lifetime license, and they included a link to a paid program that is supposed to convert Incredimail to Outlook. Incredimail says they're not endorsing it, just providing a link. The free trial version only converts 25 messages per folder, and only works with the modern version of Incredimail. If you are somehow still running XE (...how? It requires the ancient version of Flash), you'll want the older converters Thunderbird links in their how-to page.
That version only works for Incredimail2.5 and if you're running Incredimail2.0, you have to go to their other website for a completely different program. The base price is the same, but that version isn't discounted and only handles 15 messages per folder in demo mode.
I do think it's ridiculous that Incredimail never simply fixed their software to allow native export.
I also found another paid program that claims to convert Incredimail .cab files to .eml, but I do not trust it. There are no third-party reviews anywhere.
WinRAR will extract the .cab files, but it doesn't convert the messages and other data from Incredimail's formats. My archives are from about ten years ago, so they're still in the older format. IncrediConvert (ic.zip, linked from Thunderbird's page above) looks for the attachments folder and the .imh and .imm files to convert to .eml files.
I always turned off the notifier and sounds and animations in Incredimail, because I found them unneccessary and distracting. I do not know of any way to add the animations and notifiers, though I suppose someone who cares enough could code addons for Thunderbird to do that. Thunderbird does have a notification popup (optional, I have it turned off on mine) for new messages, but it's just a box.
The Skin I used was just to turn everything my favorite color, which I can now do for most programs just by setting my Windows Themes to my preferred colors. I have not used any of the Themes for Thunderbird, so I don't know how they compare to Incredimail's Skins. I don't know whether there are sounds with those Themes or not, but surely Windows Themes could put sounds to some of the things for which you want audio notification.
You can create HTML mail if you really want it. As much as I liked Incredimail's fancy stationery, I found it's not really worth it, given so many people disable HTML email. I have Thunderbird set to block external images because spammers use them to verify your email address and vandals use them to transmit viruses. The biggest thing here is that I don't know how much of the image and font data was stored on Incredimail's servers and how much was stored locally on our computers. If your recipient doesn't have the font you used in your HTML mail, it won't display properly. The computer will try to substitute the closest thing it can guess, but you have no way of knowing if the person you're emailing is seeing exactly what you sent. This is why web designers generally stick to common fonts for their websites. You could also send the recipient the font file, but that is illegal if you don't have distribution rights for that font. Besides, most people don't care enough to install a new font just to read your email in a fancy typeface.
Functionally, Thunderbird has IMAP and POP3 options, as well as the creation of filters and folders. The fact that Thunderbird has a Portable version makes it very easy to back up and move. The Import/Export addon works in either Portable or Desktop version. Also, it's free.
I don't know what exactly will happen when Incredimail shuts down their servers, but I can say that Incredimail (the program) currently can run on Windows without internet connection. This means you can still read the messages that are saved to your computer with POP3. This could mean more time to do the conversion, unless they have a time-limited kill-switch buried in the code. There's no good reason for them to do that, but there wasn't really a good reason for them to make it so hard to migrate out of Incredimail, either. I don't recommend chancing it unless you have no other choice.
If you're using IMAP, that may be easier because it usually leaves the messages on your email server. If that's the case, Incredimail won't be able to access them without internet connection, but your new email client should be able to access them directly from the email server without bothering with conversion. Check your email on your email provider's website using a browser to see if it's all there. You cannot upload to IMAP with Incredimail, so if the messages are not still on the server, you'll have to make sure they're saved on your computer and export them with a converter as above.
Incredimail does have a built-in Export for Contacts. It saves as .csv (Comma Separated Values) which is easily opened in a spreadsheet like Excel, LibreOffice, or OpenOffice. It should be just as easy to import into your new email client, but I haven't tried it because I don't really use address book functions.
For the stationery, I don't know a lot. Trying to compose a new message with my newly installed Incredimail with newly imported .cab archives shows the various old letter styles listed as options, but none of the actual image and font data - I'm guessing that had to be on Incredimail's servers, then. Interestingly, the messages in my inbox and sent folders still keep the backgrounds and fonts and sounds they had when they were sent, and they offer me the option to add to my Stylebox. It doesn't seem to stay in the Stylebox, though.
If I'm not connected to the internet, it hangs at the end of the Add to Stylebox process, so it's still trying to talk to Incredimail's servers for the stationery. The same goes for trying to add stationery files I have saved in my backup archives. In either case, if I am connected to the internet, it seems to go right in, but when I shut down Incredimail and restart it, they are no longer in the Stylebox. Right-clicking a message in my sent folder or inbox and selecting Find in Stylebox will let me create a message with that stationery, but it doesn't seem to stay in the Stylebox without Incredimail's servers.
Even the options that display in the Stylebox with images are not actually there unless they're in my inbox or sent folder. Clicking one of those asks to download, which then fails because apparently Incredimail has already disabled that server. Saving the images manually is going to be the only way to keep these, then, and only the ones that are actually saved to your own computer already. Save your message data first, then worry about optional images.
Some of my archive files contain folders of Emoticons, so those also can be manually saved, if it's important to you. Re-using those in your new email client is just a matter of including the image (in this case, an animated gif or static jpg) when you compose an email. Again, people may have those turned off or blocked, so they may not see it. Leave these optional images until after you've saved your message data.
Two weeks is a ridiculously short notice, but at least they waited until after the holiday season, unlike YahooGroups. This is the tax preparation and education services' busy season instead. Hopefully everyone will be able to salvage all the important data. Best of luck to all!
originally posted on minds.com before they decided I was a spammer and banned me