First of all, what are PMs?
It means: Private Messages
And PMBs stands for: Private Message Boards
At freelance sites, you can communicate with buyers either using PMs or PMBs. Some sites have both these options where some have just one of them.
The main question: Can you give buyers any kind of contact info [like emails, phone numbers etc] in the communication via PMs or PMBs?
Absolutely Not:
At least at the freelance sites that I know, service providers or the buyers cannot share their contact info with each other.
At some sites you will get buyer’s contact info once the buyer awards you the job.
It is possible that a freelance site will ask you to only use their own messaging system for all communications. When users use the freelance site’s internal messaging system for all their communications, then if that project enters arbitration, all the communication will become evidence and can prove which party [buyer or the service provider] is right candidate to win the arbitration.
Just read the TOS [Terms of Service] at the freelance site where you work:
Posting your contact info in PMs or PMBs will result in a temporary or permanent suspension of your account.
However, I would like to talk about one exception. At Freelancer(dot)com: you may post your contact info If The Project Is a Featured Full Time Project. And it is possible that some other sites will also such exception. You can find this info via reading the Terms of Service of the freelancing site where you work.
