EOL - Users being redirected to the incorrect OWA URL

After implementing an Exchange Hybrid configuration, it was noted that users were being redirected to the incorrect URL when connecting to OWA. Looking at the organisation relationship we can see that the TargetOwaUrl is configured with the incorrect domain name. 

[PS] C:\Windows\system32>get-OrganizationRelationship | FL

RunspaceId            : xxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

DomainNames           : {xxxxxxxxxx.mail.onmicrosoft.com}

FreeBusyAccessEnabled : True

FreeBusyAccessLevel   : LimitedDetails

FreeBusyAccessScope   :

MailboxMoveEnabled    : True

MailboxMoveDirection  : None

DeliveryReportEnabled : True

MailTipsAccessEnabled : True

MailTipsAccessLevel   : All

MailTipsAccessScope   :

PhotosEnabled         : True

TargetApplicationUri  : outlook.com

TargetSharingEpr      :

TargetOwaURL          : http://outlook.com/owa/INCORRECTDOMAIN.COM

TargetAutodiscoverEpr : https://autodiscover-s.outlook.com/autodiscover/autodiscover.svc/WSSecurity

OrganizationContact   :

Enabled               : True

ArchiveAccessEnabled  : True

AdminDisplayName      :

ExchangeVersion       : 0.10 (14.0.100.0)

Name                  :

DistinguishedName     : CN=On-premises to O365 -

                        xxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx -,CN=Federation,CN=MHC,CN=Microsoft

                        Exchange,CN=Services,CN=Configuration,DC=DOMAIN,DC=lOCAL

Identity              : On-premises to O365 - xxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

Guid                  : xxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

ObjectCategory        : domain.local/Configuration/Schema/ms-Exch-Fed-Sharing-Relationship

ObjectClass           : {top, msExchFedSharingRelationship}

WhenChanged           : 07/02/2019 11:05:05

WhenCreated           : 07/02/2019 11:05:03

WhenChangedUTC        : 07/02/2019 11:05:05

WhenCreatedUTC        : 07/02/2019 11:05:03

OrganizationId        :

Id                    : On-premises to O365 - xxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

OriginatingServer     : DC01.DOMAIN.local

IsValid               : True

ObjectState           : Unchanged

   

To resolve this we simply updated the TargetOwqUrl with the correct domain name:

Get-OrganizationRelationship | Set-OrganizationRelationship -TargetOWAUrl http://outlook.com/owa/CORRECTDOMAIN.COM

We then implemented a webmail CNAME for example, webmail.domain.com which redirects to mail.office365.com and informed the users to use this URL.

If users still continue to receive errors please ensure they have cleared their browser cache.