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Restrictions on sending and receiving email attachment files with some extensions (Updated)

FAQ (Frequently Asked Questions)

Updated: August 09, 2018
June 30, 2016

Files with the following extensions cannot be sent or received as attachments using the MailHosting service and ECCS email system due to urgent security measures.

The following extension has been added since August 9, 2018

We apologize to ECCS users as the restriction was put in place without any prior notices due to the urgency of the problem.

When you try to send an email with the relevant files from an external server, the following error message will be returned.

 510 Block For Spam

An error email will be returned to the sender if the email was sent in the normal manner. The email in question will be considered as spam and moved to spam quarantine folder in the mailbox. Please see "Change method of dealing with quarantined spam emails" (currently available only in Japanese) for Alias or emails delivered to the mailing list.

Note that there is also a risk of getting infected by viruses or information being leaked, etc. when you send or receive email attachment files with other extensions such as zip, doc, or pdf. The above-mentioned filtering is just a solution to slightly reduce those risks. Please be careful when handling email attachment files as targeted email attacks which cannot be distinguished between suspicious emails and legitimate ones are increasing rapidly.