Add space between emails in string

Dear all, 

I'm currently trying to create a mail (using mailto: ... ) to multiple email addresses within one mail. Currently all relevant mail addresses are in a string. The challenge is, that the string has no spaces between the mail addresses and therefore is not interpreted as separate recipients in the local mail application. 

# I'm starting with a loop through a set of business partners

for partnerLoop in unique(this.CampaignEventContacts.Contacts.Partner) do

# create a variable which is used in the openURL function to insert the recipinets

let partnerMail := partnerLoop.Contacts.Email;

Challenge: 

The to-line in the mail application looks like this:

name1@provider1name2@provider2name3@provider3

Ask: I'm looking for a method to insert a space between the single mail addresses. 

Thanks for you support in advance

Robert