Solving non-SMTP Address Issues

Document created by user.oxriBaJeN4 Employee on Nov 2, 2016
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Mimecast uses the addresses in message headers to:

  • Populate end user Mimecast mailboxes.
  • Ensure the SMTP address end users log in with has the required access permissions.


If your ingestion data is organized:

  • In a single instance by date, failure to resolve non-SMTP addresses for your end users results in them being unable to access these messages in Mimecast.
  • Per user with all files named by the end user primary SMTP addresses, the end user is granted permission to the messages based on the filename.


Regardless of your data’s organization, the best end user experience is when non-SMTP addresses are resolved to SMTPs during the ingestion process.


Many mail systems store messages using x400 addresses rather than SMTP addresses. Where this happens, the message headers from Exchange contain a user’s Legacy Exchange Distinguished Name (LEDN) instead of SMTP. For example:





All accounts in Active Directory with x400 addresses are automatically resolved during the ingestion process. However we are unable to resolve x400 addresses of accounts that no longer exist in Active Directory (e.g. previous staff members).




An internal message from User A (current staff member) to User B (ex-staff member) is being ingested into Mimecast account. User A's address is resolved by your Active Directory server, but User B's address is not, and has been IMCEA encapsulated.


The following is displayed in the Archive Search result page:

  • From: User A
  • To: User A


This is despite the header containing the following:

  • From: User A
  • To: User B


When searching the Archive Search for messages to or from the unresolved user, you’ll have to:

  • Search for part of the unresolved address string (e.g. "User B").
  • Select the “Search Headers” option.


You’ll be unable to search on the SMTP address for that user in the “To” or “From” search fields, because Mimecast won’t know the SMTP address.