We rejoined after a few years. Is there any way to delete messages from a few years ago, or indeed recent ones that are no longer needed?
Hello @John_Jane and a very warm welcome to the Community Forum 
I have attached a thread you might want to take a look at with regards to your question
For reference, as a member, you can also add your TrustedHousesitters profile on to your Forum profile by following the attached link, should you wish. This will then enable others to offer you helpful advice and feedback.
If you are unsure how to do this, or if you have any questions at all, do not hesitate to ask, we are all more than happy to help.
Also, remember you can use the spyglass symbol at the top of the page next to the TrustedHousesitters logo and search for any questions that you may have as they have most likely already been answered on here and of course if not then please just ask! 
I think the short answer is: This is an antiquated messaging system. It would cost money to update and customize.
The takeaway is: Sort through everything that should be deleted. Give it all a label. Put it in archive.