ActiveSync on OS 11.2.6

Started a ActiveSync session:

#1: Header received:

X-MS-PolicyKey = "0"
Accept-Language = "de-de"
User-Agent = "Apple-iPhone8C4/1504.100"
Accept = "*/"
Connection = "close"
Content-Length = "0"
Accept-Encoding = "br, gzip, deflate"
Host = "mail.***.de"
User = "\t1@***.de"
Password = "*"
Query = "OPTIONS /sync.php/Microsoft-Server-ActiveSync HTTP/1.1"
Authorization = "Basic *"

#1 Header send:

Response = "HTTP/1.1 200 OK"
Cache-Control = "private"
Accept-Charset = "UTF-8"
Allow = "OPTIONS, POST"
Public = "OPTIONS, POST"
Server = "sync*gw server"
MS-Server-ActiveSync = "7.07.51"
MS-ASProtocolVersions = "2.5,12.0,12.1,14.0,14.1,16.0,16.1"
MS-ASProtocolCommands = "Sync,GetAttachment,FolderSync,FolderCreate,FolderDelete,FolderUpdate,MoveItems,GetItemEstimate,Search,Settings,Ping,ItemOperations,Provision,ResolveRecipients"

#2 Header received:

Connection = "close"
User-Agent = "Apple-iPhone8C4/1504.100"
Content-Length = "110"
Content-Type = "application/vnd.ms-sync.wbxml"
Accept-Encoding = "br, gzip, deflate"
Accept-Language = "de-de"
X-MS-PolicyKey = "0"
MS-ASProtocolVersion = "16.1"
Accept = "*/"
Host = "mail.***.de"
User = "\t1@***.de"
Password = "*"
Query = "POST /sync.php/Microsoft-Server-ActiveSync?User=t1@***.de&DeviceId=O8S9UD4DOH0SLEPOQC5AJ9AE3C&DeviceType=iPhone&Cmd=Settings HTTP/1.1"
Authorization = "Basic *"

#2 Body received:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:AirSync PUBLIC "-//ActiveSync//DTD AirSync//EN" "">
<Settings CHARSET="UTF-8" xml-ns="activesync:Settings">
  <UserInformation>
    <Get/>
  </UserInformation>
  <DeviceInformation>
    <Set>
      <Model>iPhone8C4</Model>
      <OS>iOS 11.2.6 15D100</OS>
      <UserAgent>iOS/11.2.6 (15D100) dataaccessd/1.0</UserAgent>
      <FriendlyName>iPhone SE</FriendlyName>
      <OSLanguage>de-DE</OSLanguage>
    </Set>
  </DeviceInformation>
</Settings>

#2 Header send:

Response = "HTTP/1.1 200 OK"
Cache-Control = "private"
Accept-Charset = "UTF-8"
Connection = "Keep-Alive"
Content-Type = "application/vnd.ms-sync.wbxml; charset=UTF-8"
Content-Length = "61"
MS-Server-ActiveSync = "7.07.51"
Date = "Sun, 01 Apr 2018 08:13:46 GMT"

#2 Body send:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:AirSync PUBLIC "-//ActiveSync//DTD AirSync//EN" "">
<Settings CHARSET="UTF-8" xml-ns="activesync:Settings">
  <Status>1</Status>
  <!-- Success. -->  
  <DeviceInformation>
    <Status>1</Status>
    <!-- Success. -->
  </DeviceInformation>
  <UserInformation>
    <Status>1</Status>
    <!-- Success. -->
    <Get>
      <Accounts>
        <Account>
          <AccountName>t1@***.de</AccountName>
          <UserDisplayName>t1@***.de</UserDisplayName>
        </Account>
      </Accounts>
    </Get>
  </UserInformation>
</Settings>

#3 Header received:

Connection = "close"
User-Agent = "Apple-iPhone8C4/1504.100"
Content-Length = "20"
Content-Type = "application/vnd.ms-sync.wbxml"
Accept-Encoding = "br, gzip, deflate"
Accept-Language = "de-de"
X-MS-PolicyKey = "0"
MS-ASProtocolVersion = "16.1"
Accept = "*/"
Host = "mail.***.de"
User = "\t1@***.de"
Password = "*"
Query = "POST /sync.php/Microsoft-Server-ActiveSync?User=t1@***.de&DeviceId=O8S9UD4DOH0SLEPOQC5AJ9AE3C&DeviceType=iPhone&Cmd=Settings HTTP/1.1"
Authorization = "Basic *"

#3 Body received:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:AirSync PUBLIC "-//ActiveSync//DTD AirSync//EN" "">
<Settings CHARSET="UTF-8" xml-ns="activesync:Settings">
  <Oof>
    <Get>
      <BodyType>TEXT</BodyType>
    </Get>
  </Oof>
</Settings>

#3 Header send:

Response = "HTTP/1.1 200 OK"
Cache-Control = "private"
Accept-Charset = "UTF-8"
Connection = "Keep-Alive"
Content-Type = "application/vnd.ms-sync.wbxml; charset=UTF-8"
Content-Length = "22"
MS-Server-ActiveSync = "7.07.51"
Date = "Sun, 01 Apr 2018 08:13:47 GMT"

#3 Body send:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:AirSync PUBLIC "-//ActiveSync//DTD AirSync//EN" "">
<Settings CHARSET="UTF-8" xml-ns="activesync:Settings">
  <Status>1</Status>
  <Oof>
    <Get>
      <OofState>0</OofState>
      <!-- Oof is disabled -->
    </Get>
  </Oof>
  <!-- Success. -->
</Settings>

#4 Header received:

Connection = "close"
User-Agent = "Apple-iPhone8C4/1504.100"
Content-Length = "13"
Content-Type = "application/vnd.ms-sync.wbxml"
Accept-Encoding = "br, gzip, deflate"
Accept-Language = "de-de"
X-MS-PolicyKey = "0"
MS-ASProtocolVersion = "16.1"
Accept = "*/"
Host = "mail.***.de"
User = "\t1@***.de"
Password = "*"
Query = "POST /sync.php/Microsoft-Server-ActiveSync?User=t1@***.de&DeviceId=O8S9UD4DOH0SLEPOQC5AJ9AE3C&DeviceType=iPhone&Cmd=FolderSync HTTP/1.1"
Authorization = "Basic *"

#4 Body received:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:FolderHierarchy PUBLIC "-//ActiveSync//DTD FolderHierarchy//EN" "">
<FolderSync CHARSET="UTF-8" xml-ns="activesync:FolderHierarchy">
  <SyncKey>0</SyncKey>
</FolderSync>

#4 Header send:

Response = "HTTP/1.1 200 OK"
Cache-Control = "private"
Accept-Charset = "UTF-8"
Connection = "Keep-Alive"
Content-Type = "application/vnd.ms-sync.wbxml; charset=UTF-8"
Content-Length = "70"
MS-Server-ActiveSync = "7.07.51"
Date = "Sun, 01 Apr 2018 08:13:49 GMT"

#4 Body send:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:FolderHierarchy PUBLIC "-//ActiveSync//DTD FolderHierarchy//EN" "">
<FolderSync CHARSET="UTF-8" xml-ns="activesync:FolderHierarchy">
  <Status>1</Status>
  <!-- Success. -->
  <SyncKey>1</SyncKey>
  <Changes>
    <Count>1</Count>
    <Add>
      <ServerId>A1</ServerId>
      <ParentId>0</ParentId>
      <DisplayName>Persönliches Adressbuch</DisplayName>
      <Type>9</Type>
      <!-- Default Contacts folder -->
    </Add>
  </Changes>
</FolderSync>

#5 Header received:

X-MS-PolicyKey = "0"
Accept-Language = "de-de"
User-Agent = "Apple-iPhone8C4/1504.100"
Accept = "*/"
Connection = "close"
Content-Length = "0"
Accept-Encoding = "br, gzip, deflate"
Host = "mail.***.de"
User = "\t1@***.de"
Password = "*"
Query = "OPTIONS /sync.php/Microsoft-Server-ActiveSync HTTP/1.1"
Authorization = "Basic *="

#5 Header send:

Response = "HTTP/1.1 200 OK"
Cache-Control = "private"
Accept-Charset = "UTF-8"
Allow = "OPTIONS, POST"
Public = "OPTIONS, POST"
Server = "sync*gw server"
MS-Server-ActiveSync = "7.07.51"
MS-ASProtocolVersions = "2.5,12.0,12.1,14.0,14.1,16.0,16.1"
MS-ASProtocolCommands = "Sync,GetAttachment,FolderSync,FolderCreate,FolderDelete,FolderUpdate,MoveItems,GetItemEstimate,Search,Settings,Ping,ItemOperations,Provision,ResolveRecipients"

#6 Header received:

Connection = "close"
User-Agent = "Apple-iPhone8C4/1504.100"
Content-Length = "13"
Content-Type = "application/vnd.ms-sync.wbxml"
Accept-Encoding = "br, gzip, deflate"
Accept-Language = "de-de"
X-MS-PolicyKey = "0"
MS-ASProtocolVersion = "16.1"
Accept = "*/"
Host = "mail.***.de"
User = "\t1@***.de"
Password = "*"
Query = "POST /sync.php/Microsoft-Server-ActiveSync?User=t1@***.de&DeviceId=O8S9UD4DOH0SLEPOQC5AJ9AE3C&DeviceType=iPhone&Cmd=FolderSync HTTP/1.1"
Authorization = "Basic *"

#6 Body received:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE activesync:FolderHierarchy PUBLIC "-//ActiveSync//DTD FolderHierarchy//EN" "">
<FolderSync CHARSET="UTF-8" xml-ns="activesync:FolderHierarchy">
  <SyncKey>0</SyncKey>
</FolderSync>

Synchronization ends up with looping between #6 and #4.

#6 is not according to ActiveSync protocoll: Android and other software client then sends - as expected - a <Sync> request for folder...

Does anybody know what is wrong??