A frequent question I receive is how to monitor the availability of BPOS and how to access BPOS service notifications.   There's a few good techniques and resources out there.  In my experience, BPOS availability has been great and I've only had one issue since August 2008 when I started using it. It cleared up within a minute or two.  Here's a couple of good tips:

Monitoring BPOS

There's a few different ways to monitor your BPOS service.  If you own a monitoring tool such as Solar Winds' IPMonitor (http://www.solarwinds.com/products/ipmonitor/) you can easily configure fairly sophisticated queries against your various BPOS service URLs such as SharePoint sites or OWA.  I generally configure some alerts againsts my SharePoint sites and OWA.  In the use of your BPOS service you also rely on either your own DNS hosting infrastructure or perhaps a third parties.  I set up QoS monitoring on all my DNS servers - remember if DNS is not working properly mail flow, your website and other services may not function as you have designed.  You can also probably monitor SMTP by configuring a dedicated user (consuming a license) and using an SMTP monitoring rule that can be configured to support authentication (these are available in the IPMonitor product). 

BPOS Service Notifications

BPOS Service Notifications are another great way to keep in touch with Microsoft annouced service issues or maintenance. 

North America Microsoft Online Services Standard RSS Feed https://rss.microsoftonline.com/

APAC Microsoft Online Services Standard RSS Feed https://rss.apac.microsoftonline.com/

Europe Microsoft Online Services Standard RSS Feed https://rss.emea.microsoftonline.com/ 

Message Filtering RSS Feed http://rss.messaging.microsoft.com/ 

Microsoft recently upgraded the BPOS mailbox storage limit from 5GB to 25GB. While new users get the 25GB limit automatically, you need to manually upgrade your existing users to take advantage of the new limit. This short tutorial will show you how: http://www.screencast.com/t/NzM5NjEwZDEt

I was having a conversation with the Bamboo Solutions folks at their booth at the SharePoint Conference 2009 in Las Vegas, NV USA.  We started discussing custom solutions and web parts on BPOS.  Part of SharePoint 2010's core capabilities include the ability of a Site Collection Administrator to upload WSP's.  Obviously there would a huge set of limitations since BPOS Standard is essentially a shared hosting offering built around WSS 3.0 and SharePoint Foundation configured in some varient of Host Header Mode / Host Named Site Collections.  Well BPOS SharePoint 2010 is pretty cool because it brings in a bunch of features from SharePoint Server 2010 including My Sites!  It also brings that custom solution file upload for Site Collection Administrators. The BPOS folks at Microsoft during one of their sessions started discussing the QA/QC process for allowing custom solutions on BPOS-D (dedicated).  Great. Awesome news. But probably the set of limitations is so long that most of us still need to run a non-BPOS SharePoint farm somewhere. 

Well here's the thought for the day - how about BPOS support for BLOB storage? Looking at Storage Point or AvePoint's free blob storage utility this seems like it could be a really interesting combo with S3 or Azure.  I look for all your feedback!