Outlook users have taken to Twitter to report problems with e-mails not sending and login issues.

Independent website Down Detector has registered a peak of 874 Outlook users experiencing issues with the service today.

Independent website Down Detector registered a new peak of 1,435 users experiencing issues with Outlook, and are still receiving hundreds of reports the e-mail service is down.

One of those users who reported that Outlook is down is respected film critic Mark Kermode.

Although you calendar will automatically request an update from the Timetastic feed, the timescales can be somewhat unclear and occasionally calendars seem to stop updating or have large delays - we've seen as much as 1-2 days.

I wish we could provide something more concrete on this subject, but it's the one area that seems to crop up occasionally and is both hugely very frustrating (for both you and us) yet there is little we can do.

Some 54 per cent of those users experienced issues with login while 45 per cent had problems with the Outlook website in general.

Down Detector measures social mentions around certain topics to track outages across the globe.Unfortunately resolution of this issue tends to be a waiting game: An important aspect to understand about ical feeds: It is your calendar application (Outlook, Google, Apple, etc etc) which periodically requests an update of the information from Timetastic i.e.Timetastic does not push the data to you calendar, it's your calendar that requests it from Timetastic.“We've redirected requests to alternate infrastructure to restore service, and we're monitoring the environment while connectivity recovers.“Additionally, we're investigating an issue in which users are unable to send email messages.”The Outlook Twitter account has also been telling users that a fix is currently being worked on.UPDATE FIVE: Microsoft have spoken out about the outage affecting Outlook users today.