Mac mail slow due to 65gb of email? Ive got 8 email accounts which i manage in mac mail. 

The largest one of these accounts is 30GB and the others are each c. 5GB. So 65GB in total. Most of these are google apps for business accounts, and one is a private imap system.

I feel that the size of the email accounts is making the mac mail programme slow. 

Is there anything i can do to make mac mail run better with these large files. 

I have seen some other email clients that have a feature where you can only sync the last X years of emails to the desktop client whilst keeping the rest of the older emails on the email server, dose mac mail have something similar ?
Mac Mail saves the emails on the hard drive. I would try to find A mail app that doesnt save the mail to the hard drive but just sees the mail from the cloud email server. 

If you use Gmail as a mail client for those emails then I recommend Mailplane. Others like Spark, CanaryMail, Mailspring and Polymail are all good alternatives along with others in the Mac App Store.

Other email clients should offer an option to store less emails offline and limit the size of your cache to a manageable size.

While there are steps to clean out the space for Mac Mail, I personally think signing out of it altogether and using an alternative might be best.