We’re launching MailChimp v5.3 late tonight. The changes are big, but they won’t require any reboots of the server or anything that would affect scheduled email campaigns or reports. While we’re launching, you may not be able to log in to the service. We plan to begin around 10PM ET (see this in your timezone), and the upgrade process should only take a few hours (if all goes well). The changes might take some time to propagate to all user accounts, but by 9am ET tomorrow, all accounts should be upgraded.

Here’s what’s in v5.3…

• Social Pro Add-on is free until March of 2011. Yes, you heard that right. Normally, SocialPro costs an additional 20% of whatever you’re paying for MailChimp. But for 6 months, we’ll cover that cost. This is a huge investment for us, but we’re committed to helping our customers get more social and be more human with their email marketing. Learn more about Social Pro here.
• AIM Reports are free – We silently rolled this out a couple weeks ago, but now it’s official. Our AIM reports add-on is being absorbed into our default feature set, and is therefore now free (yay!). The data’s found in your campaign reports under “subscriber activity.” For those of you who don’t know, AIM reports was an add-on that cost $49, and basically gave “who did what” stats. We made AIM free so that we can make the upcoming Golden Monkeys app (which requires AIM), free. Double yay!
• Freemium Plan expanded – One year ago, we launched our freemium plan, allowing businesses with less than 500 subscribers to use MailChimp free of charge. We grew from 85,000 users to more than 440,000 users. So yeah, that worked. Now, we’re expanding our freemium plan to allow customers with lists up to 1,000 members to use MailChimp free. Spread the monkey love!
• MailChimp Faces – If you have the Social Pro add-on enabled for your list (ahem, which is free until March), you’ll be greeted by your subscribers’ avatars every time you sign in to the MailChimp Dashboard. Learn more about MailChimp Faces.
• Add Facebook Comments to Emails – The discussion doesn’t have to end when you click “send.” Add the Facebook comments button, and your subscribers can keep the conversation going. See how it works.
• Klout Scores added to member profiles – Klout analyzes your twitter and facebook accounts and rank your influence (here’s a report on @MailChimp). It’s sorta become the standard for measuring influence. So we’ve added Klout scores into all MailChimp member profiles.
• Like Button enhancements – Back in July, we introduced the Like button to email marketing. Some of you told us you wanted more flexibility with it. So we added the ability for you to insert the URL that you want “liked.” Your subscribers can like a product inside your campaigns, an item inside your RSS-to-email, or even your Facebook page. Basically, it’ll work like this: * |FACEBOOK:LIKE:URL| *
• Tweet Button – Campaign archives will include the “Tweet this” button, and you can insert a tweet this merge tag into your campaigns. RSS campaigns will get a tweet merge tag for each item, such as * |RSSITEM:TWITTER| *  (we’ll post more details, don’t worry)
• Buzz Button – We’ve added a merge tag for Google’s Buzz button, as well as one for items in an RSS campaign.
• Facelift & Botox Treatment – Over the years, we’ve been innovating like hell — adding features on top of features on top of features. We decided it was time to sit down, take stock of our UI, and optimize like hell. Our interface elements are more consistent, fonts are refined, icons are more elegant, CSS files were reduced by nearly 80k and things are just — well, more “aaaaaaaaaah.”
  
• Signup forms redesigned – We’ve redesigned the entire signup process. Signup forms, thank you pages, and welcome emails are more elegant and simple, and with a little sprinkling of CSS3. There’s a new button in the signup form creator that will automatically design your signup form for you (it pulls in CSS and color settings from your website). Finally, signup forms are now optimized for mobile display (they’ll auto-zoom on iPhone and Android). Existing signup forms are not changing. This is for signup forms moving forward (and you’ll have the option to use “old” forms vs. “new” forms).

We’ll be posting details about all the new features (especially all the new social merge tags) shortly after we launch.

Plus, we’ll have even more exciting news for our customers to announce tomorrow, so stay tuned! Weeeeeeeee!

[UPDATE: 9-16-2010, 12:19PM ET]

• We launched on schedule last night, but experienced a backlog in campaigns within a few hours. The backlog is slowing down test sends, and all email delivery in general. We’re seeing test sends take around 30 minutes. This should improve soon, as our delivery queue clears out. Yes, this is a complete p.i.t.a. when you’ve got to test something for a campaign that’s due now. We’re sorry for the inconvenience.
• Around 10am, some users experienced an outage for roughly 20 minutes. That was due to a process that started (good), but never stopped (bad), which just overloaded the system. We’re back online and normalized now, but are still working through the delivery queue to speed things up. If your campaign was affected, contact our support team for make-goods. If you’re a competing ESP who serves the “mid market” and who is desperately calling on our clientele to switch away from MailChimp, they’ve asked me to tell you to stop, because it’s annoying and kinda needy. Just send us a box of your company brochures, and we’ll happily ship them out to our larger customers for you (it’s less spammy that way).
• Some customers are asking where the new Facebook Comments feature is. Sometime yesterday, Facebook broke the interwebs with that. Here’s their bug report. It’s sort of a simple little issue they’re experiencing (if I understand correctly, an “onFocus” UI sorta thing), and we suspect they’ll resolve it soon. But until then, we’re leaving the feature turned off.
• As always, stay tuned to our twitter account: @mailchimpstatus for the critical updates, or @mailchimp for general updates.

[UPDATE: 9-16-2010, 7:42PM ET]

• The queue is finally getting back to normal. It’s okay to send emails, but you still may see some delays. Just not as drastic as earlier today.
• During the day, we also had a brief outage that rebooted one of our delivery servers. That caused it to send duplicate emails for some of our customers. We’ve stopped the duplicate sending, but if your account was affected, please contact our support team so we can make it up to you.
• Our latest tweet was that things would be calming down by 8pm ET. We’re on track. Earlier, we had a lot of “jobs” waiting to be picked up by a heavily backlogged queue. Now, there are no more jobs waiting. We’ve still got a heavy queue of emails to go out, but we’re churning through them at faster than normal (but not fast enough to hurt deliverability) speeds. Our staff will be monitoring servers throughout the night.

[UPDATE: 9-16-2010, 9:14PM ET]

• Today’s been an extremely high volume day. Lots of peakiness. At around 8:30pm, just when we expected things to calm down, we had another surge of email volume that caused another brief outage. On the bright side, that was the last big surge for today, and now that we’re through it, things are calming down. Sending is still a little slow, but we’re starting to see the light at the end of the tunnel. Thanks for your patience, and we just can’t apologize enough for this inconvenience. Very, very sorry. We’ll continue to monitor things throughout the night.

[UPDATE: 9-17-2010, 8:40AM ET]

As of 6:47am ET, things appear to be back to normal. The RSS-to-email and autoresponder campaigns that we trickled out overnight have all been sent. Our delivery queues are back down to normal levels.  If you have a campaign that did not get sent, please contact support, and we’ll look into its status for you. Thanks for your patience throughout all this.

Summary of what happened yesterday…