After migrating to 0365 - How to inform the suppliers and organisations that email address has changed.


We have Exchange 2007 and the current email address format is and we are going to change the email domain when migrate to 0365 in few months.

Once the migration has happened the current email format will change from TO

I have been asked how to inform our suppliers that our email address has changed (any automated ways to inform the change of email address).

Bit worried how this is going to work after migration if any one send the email to and bounces back it will be a problem.

Please suggest is these any way within 0365 to automate this process.
Any help and suggestions much appreciated.
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When you register new domain to O365, register old and new domains to o365
The O365 user will have both old and new email associated with and his primary email would be on new domain and would be able to receive emails on both domains. You can add or ask users to add side note in their email communication about new email address and inform ur customer this for at least 3 month
After that you may remove old domain or not , user primary smtp will be with new domain only
There won't be any outage
U need to set mail flow correctly
Add new smtp domain as accepted domain at onpremise and o365 both place
Add new email address policy pointing to new domain and make that address as secondary
Sync your all onpremise accounts to cloud this way
Now once you migrated 1st mailbox to cloud, change onpremise account primary smtp and UPN to match new domain and add forwarding to on microsoft id and sync it to cloud
Now whoever send email to, will get forwarded to his cloud mailbox
If anybody send email to, mail will directly received in o365 mailbox
This way u will migrate all mailboxes without any issues
Once you finish migration, inform parties in mail signature about new email address for say 3 months and then u may keep / remove old domain and SMTP

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Mahesh is all over this!  He is so correct. Simply add both SMTP domains to O365 during your migration then notify recipients of the pending email change by a custom footer note. If you are nervous, just keep the old SMTP address suffix as secondary.
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lianne143Author Commented:
How do I add a custom foot note to notify recipients of the pending email change.
Please post tutorials.
No special.config
Ask migrated user to add message in signature about new email address change and how long old email would be there
That's all I believe
U may add disclaimer in every outgoing mail if wanted to which add sender email address dynamically via variable
U can find lots tutorials how to set per user variable in disclaimer
FOXActive Directory/Exchange EngineerCommented:
Below is the read to add the disclaimer to the outgoing messages.  
ref link:

However, I would go with an automatic reply for your scenario. This reply will go out for anyone that is emailed
1.  Connect to your o365 environment with powershell
2.  Get-Mailbox -ResultSize Unlimited | %{Set-MailboxAutoReplyConfiguration $_.Alias -AutoReplyState Enabled -ExternalMessage "I have changed my email address.  This reply has the new email address I am using, please update." -InternalMessage $Null
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