Greetings, fellow trailblazers,
I'm in a situation where xxx's personal email address will be updated to their work email address. Our current approach involves utilizing the SUBSCRIBER RELATIONSHIP as follows:
Contact: MC Subscriber key is linked to Subscribers via the Subscriber Key, where Contact: MC Subscriber key represents the subscriber key (country code _email address).
I'm seeking guidance on the most effective method for sending future communications to the work email address. Are there any potential obstacles you foresee in this approach?
a) Replace the personal email address with work address
b) Anyother way?@* Marketing Cloud Engagement *
Lukas Lunow (NoA Ignite) 
Forum Ambassador
You are writing:
Contact: MC Subscriber ID is linked to Subscribers via the Subscriber Key, where Contact: MC Subscriber ID represents the subscriber key (country code _email address).
This is not really clear to me. MC Subscriber ID is a numerical value, which is autogenerated by SFMC, while MC Subscriber Key is your custom (and hopefully) global identifier. Is it correctly understood, that you use e.g. DK_john@example.com for a subscriber from Denmark? I will not recommend using email addresses as Subscriber Key, as these are not persistent. Please check this article on recommendations for choosing the most suitable ID for Subscriber Key. I know it is too late in your case, but at least you are aware of best practices.
Back to your question. You cannot use multiple email addresses for the same subscriber. It will be a highly custom solution with more drawbacks than advantages. I am writing about it in more details here.
I will recommend you to replace the personal email address with the work email address (or perhaps create yet another contact, if you want to be able to distinguish whether you want to send to a personal or work email for the same individual). You should be aware that, depending on how you are sending the emails, the email address linked to that Subscriber in the All Subscribers list will "overwrite" the email address in your sendable data extension, if they both relate to the same Subscriber Key. To ensure the latest email address is used, you will need to update it in All Subscribers, as described in this guide.
