Ability to forward emails into an existing ticket

Would really like the ability to forward emails directly into an existing ticket.

This is what I’m trying to achieve:

• Support ticket is created for a customer
• There is back and forth correspondence a number of times
• Customer then sends another email directly to my personal account - which is part of the support correspondence – but not a normal reply

• This can happen if they used another device or simply forgot to reply to the normal email thread

• I would like the ability to forward that email so that it is appended to the existing support ticket as if they had replied in the normal way i.e. it keeps attachments, the sender information, date/time, etc…

I've read the thread here https://support.zendesk.com/hc/communities/public/posts/203392746-How-can-I-forward-an-email-into-an-existing-ticket-?input_string=Ability%20to%20forward%20emails%20into%20an%20existing%20t, which has no resolve, plus I've been in touch with support and they clarified that it can't be done at present unless you make use of their API - which tells me it can be done! ;)