[ZendTo] [Feature Request custom string in subject per DropOff]

[Der PCFreak]

Hi Jules, hi all.

I have a strange request from our ZendTo users. They asked if it would 
be possible to add a custom field when sending a DropOff
that results in a custom text in all ZendTo email concerning this 
specific DropOff.

Example current:

[ZENDTO] One of the recipients has picked up your drop-off!

Example requested:

[ZENDTO] CUSTOM_STRING One of the recipients has picked up your drop-off!

I asked a little bit about the purpose of their request and they told me 
that project teams sort their email by subject and
consequently keep the project name (CUSTOM_STRING) in every subject of 
their emails concerning that specific project.
So later they could sort by project name (CUSTOM_STRING) within Outlook 
to be able to verify when they sent a specific DropOff.

Question:
Is it possible to implement such a feature?

I know that I could handcraft it but I don't want to make big changes to 
the source and always have to keep track of them when upgrading.

I am currently not on the latest version of ZendTo, so if such a feature 
is maybe already present in the latest version, feel free
to tell me.

Thanks in advance.

Peter