When you send an email and receive a delivery failure message, there could be several reasons. We've listed the most common error messages below, along with suggested resolutions. Select an error below to see more information. Can't connect to remote server/message expired Connection timed out Email could not be delivered to members from the group Errors that include "blocked" or "listed in" and references to sites like "spamcop," "dynablock," "blackhole," or "spamhaus" Host unknown or Domain lookup failed Mailbox full or Quota exceeded Mailbox not found, Invalid mailbox, or User unknown Mailbox unavailable Message too large No adequate servers Out of memory Resources temporarily unavailable Undeliverable Your message couldn't be delivered Further information about AOL Com Mail Login Sign page issue visit at https://www.theemailhelpline.com/aol-com-email-login/