Hello friends!
There is a problem we detected after our user had reported us about a problem with access to his mailbox via sogo and activesync from outlook.
For example, he sent several test messages from outlook.com to his mailbox in our server where message contains header To: =?koi8-r?B?J+HO1M/OIOHO1M/Oz9cn?= <user@domain.tld>
When we try open users Inbox in SOGo, first time we will see list of messages and it is possible open any message in this list except the test messages from outlook.com.
As soon as we try open the message sent from outlook.com, there appears "Bad gateway" pup-up message. And in sogo log we have next errors

Nov 08 16:19:43 sogod [26329]: [RM:MailerUI] LOOKUP FAILED: UIxMailPartTNEFViewer
Nov 08 16:19:43 sogod [26329]: [RM:MailerUI]   PARENT (<0x0x55c32c18c420[WEResourceManager]:>) SAID: (null)
Nov 08 16:19:44 sogod [26212]: <0x0x55c32c01fec0[WOWatchDogChild]> child 26329 exited
Nov 08 16:19:44 sogod [26212]: <0x0x55c32c01fec0[WOWatchDogChild]>  (terminated due to signal 11)
......
S[0x55c32c71b9b0]: 9 OK Fetch completed (0.010 + 0.041 + 0.009 secs).
C[0x55c32cd2a750]: 10 uid fetch 418 (body.peek[1])
S[0x55c32c71b9b0]: * 171 FETCH (UID 418 BODY[1] {108}
S[0x55c32c71b9b0]: 10 OK Fetch completed (0.012 + 0.041 + 0.011 secs).
C[0x55c32cd2a750]: 11 uid fetch 418 (body[2Nov 08 18:26:25 sogod [26212]: <0x0x55c32bfeb900[WOWatchDogChild]> child 26313 exited
Nov 08 18:26:25 sogod [26212]: <0x0x55c32bfeb900[WOWatchDogChild]>  (terminated due to signal 11)

After these errors sometime we can't login and see any page for this user, there is only "blank" page.

Can anybody help with this problem?