Delegate drafts stuck in outbox of manager forever (EXO / hybrid)

Question

Error
Certain emails are stuck in outbox of multiple senders forever

Approved workaround
Sender opens the email, reselects his exchange online email account in the from field and sends again

Context

• Different delegates prepare email drafts for different managers who try to send the drafts after editing them
• Drafts are drag n dropped directly to managers drafts folders or by mailing them to the managers as attachments (are then drag n dropped to the drafts folder by the managers)
• Turned out that at least in one negative example delegates recycle older drafts as a basis for new drafts
• Source drafts might origin from pre-hybrid times

Analysis of one negative example being stuck in the outbox

• PR_SENDER_ADDRTYPE as well as PR_SENT_REPRESENTING_ADDRTYPE both have value "SMTP"
• However PR_SENDER_EMAIL_ADDRESS, PR_SENT_REPRESENTING_EMAIL_ADDRESS and PR_SENT_REPRESENTING_SMTP_ADDRESS all contain a "/O=EXCHANGELABS/[...]" value
• How I see things that can't work together, considering the address values, address types must be "EX"

Further analysis

• I have found a potentially to be recycled draft which did show a "/o=<domain name>[...]" x500 address mouseovering the sender which is not identical with the legacyExchangeDN of the manager (sender)

Environment

• Hybrid with Exchange 2013
• Manager and delegate mailboxes are exclusively on EXO
• Outlook 2013 and 365 mixed (potentially all users might have used both Outlook versions with the same user and therefore Outlook profile)
• I think that at least the delegates exclsuively use RDS with Outlook in online mode
• In the negative example referenced above the manager did use Outlook 2013 in online mode on RDS

Questions

• What could cause the address type becoming "SMTP" although address values are type EX?
• Considering address type would be correct (EX), can I expect messages at least leaving the outbox and accepted by EXO when sender address values are "/o=<domain name>[...]" matching an x500-addresses of the sender in AAD?

Thanks in advance
Markus

Answer 1

Hi @MarkusOE

Can managers directly send mails to your internal users(without reselecting his exchange online email account?). Does the issue occured when the mails are created by delegates?

According to your information above, you are in a hybrid environment and you have migrated the users from on-prem to cloud. Have you tried changing to chched mode or using OWA to verify the result again? And I want to confirm how did you migrate your users to O365 from your on-prem server?

You may check if legacyExchangeDN are correct in O365. Please check the related links here:
The Attribute, the Myth, the legacyExchangeDN
IMCEAEX non-delivery report when you send email messages to an internal user in Office 365
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

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