Some users of Google Inc.'s Postini messaging management tools are having a bad e-mail day.Postini users have been reporting on Twitter for most of the afternoon that they're not receiving their e-mail or that its severely delayed. Andrew Kovacs, a spokesman for Google, acknowledged the Postini problem in an e-mail to Computerworld , and noted that it is affecting some, but not all, Postini customers in the U.S."We're aware of an issue that's causing a delay in mail delivery for some Postini customers in the US, and are working to fix it as quickly as possible," wrote Kovacs. "We know how important mail is to our users, so we take issues like this very seriously, and apologize for the inconvenience."Google purchased Postini Inc., which develops message security, archiving, encryption and policy enforcement tools, about two years ago.Dan Olds, an analyst with The Gabriel Consulting Group, said the problem has to be unwelcome news for Google, considering other recent highly publicized disruptions to its Gmail e-mail service and other Google Apps."Everytime a Google service goes down, the whole world knows about it almost instantly," he added. "This makes it very difficult for Google to build the kind of reputation for stability and availability that will attract large numbers of paying customers. The service has a hiccup, users question the quality of the service."Google is pointing anyone experiencing a problem to visit the Postini support portal .However, users are having troubles accessing and logging onto the support site.Like frustrated users of all technical persuasions, many Postini customers took to Twitter to vent today."Postini's redundant servers are apparently redundantally crappy," wrote one Twitterer, while another said, "postini having downtime is just really not a option. Google needs to get it's act together."Still others wrote, "Stopping mailflow into the company is NOT COOL"; "Has $GOOG lost their edge? postini has been down for 4 hours, now. This is stuff that just cannot fail," and "Seriously @google, What's the deal w\/ Postini today? Nothing online, no response from support. What gives?!"Google has taken it on the chin quite a bit in recent months because of downtime with Gmail and other Google Apps.Last month, Google News , the company's news aggregation site, crashed and then two days later Gmail users suffered through a disruption.Earlier in September, Gmail experienced a day of intermittent disruptions. Users of Gmail and other Google applications also endured well-publicized service crashes in both February and May.