Not enough space on the disk.

Causes

• Number of recipients the email message has – receiving server cannot parse which of the recipients it is supposed to deliver to.
• Out of memory condition due to a file overload.
• May depend on too many messages send to a particular domain.

Fixes

Step 1: Try Again By Sending Smaller Sets

Try again by sending smaller sets of emails instead of one big mail-out. For example, separate the big email to smaller one.

Step 2: Recipient Is The Only Receiver

Attempt a new email message to the failed recipient, ensure they are the only recipient for that message.