POP Lock errors on your shared MaximumASP Mail account

The error- "Mailbox already Locked" when using an Iphone in conjunction with another POP client to check your shared server mailbox stems from the nature of POP and how the Iphone and an outlook client will obtain locks on sa pop mailbox. Locking a mailbox when connecting via pop is actually an RFC requirement of the POP protocol. Pop is designed so that only one device at a time be it an outlook or similar client or a phone, blackberry or Iphone etc can maintain an exclusive lock on a mailbox. This is to prevent corruption of the mailbox or individual email messages. 

The first workaround is to turn off the Iphones connection to the shared mailbox while actively using your Outlook client, or to use Iphone and the webmail interface so that the POP lock error that occurs doesn't happen. With most devices or clients the Pop connection closes automatically after it completes a download, however we have seen issues with an Iphone not properly closing the connection and therefore maintaining an exclusive lock on the mailbox and its contents leading to the POP lock error to display in the outlook or other POP client on the computer. 

  The same applies if you have your outlook client set to POP mail every 1 minute, or if you have multiple outlook clients popping a single mailbox. The connections will be forced into a locked state to protect the integrity of the mailbox itself. This is not something which we can modify as it's actually a feature of the POP protocol itself.

A more popular workaround is to setup a forward on their mailbox to an alternate email address. To give you an example- you can set your outlook to POP the email address. You can  then create a second mailbox named and configure user@ to forward a copy of all messages to this second mailbox. You can then set your Iphone to pop this mailbox which will take care of the "battle" over the pop connection currently going on between the two devices.  Your Iphone can continue to maintain its SMTP connection to send out as however you'd now have the mailbox essentially replicated across the two devices.  In order to do this, you will set the incoming POP3 mail server as and the outgoing SMTP server as  By doing this, the user will receive forwarded emails to their Iphone account and send out emails using their standard account.

Article ID: 733, Created On: 1/4/2010, Modified: 6/13/2013

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