Port 587 would be used for Outgoing Mail (usually POP and maybe IMAP) by a lot of major email providers. If he can not use the email through his client (thunderbird) then it is likely a router or individual computer issue. If all of his computers have the same issue, then it is either a router problem or the needed port is being blocked by his ISP
Not arguing but more than likely it is some of the more nuanced settings in the email client. They have to be right or nothing is going to happen. He can't figure out how to port forward which tells me that he has too little knowledge to lock down a router. Now, if he's running a third party firewall, that could be blocking it.
I configure email clients for friends and relatives fairly often. The specific settings must be known and because they change from time to time, it can be difficult finding the right ones. It often becomes a trial and error process.
Does the server require authentication.
SSL or TLS, which is related to the port used.
Some email clients will automatically change settings depending on port requirements but other settings must be changed, etc.
This is why I asked if it's Comcast, Google, etc. The old account statement concerns me too. Is the account active? The OP isn't telling us if it is receiving email or can receive email.
The following link could be very helpful to the OP.
http://www.canyouseeme.org/
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