We had exact same issue. I don't have enough these silly Karma points to link it, so see the duplicate here:

Hi Arun,

I've been having the same problem, so I'm just going to write down our findings and hopefully you'll be able to get few steps forward. I still don't have perfect understanding about this online quotation builder module myself so your experience / success might vary. :)

We received 404 like you due to the fact that our installation has several test databases on the same domain. The quotation might work straight out of the box with single db-setup, but I for one haven't tested it like that. So in essence the redirect didn't work for a user because he doesn't have any (session/login cookie etc) on his browser. Odoo couldn't figure out to which installation (DB) it would redirect the client hence the url fails to redirect to the right place. It can however figure out the db you're using when clicking the link when you're logged in.

Also out of the box, I don't think the website frontend or portal modules are set "public" in the sense that one could view them without some sort of login first. This might affect things later on regarding user permissions so it's good to keep that in mind.

To remedy this issue we found another thread here it is explained how to start openerp, with the parameter that passes the db on urls. ( --db-filter ^%d$) Original source: https://www.odoo.com/forum/Help-1/question/Domain-based-db-filter-6583

Depending on your setup, your solution might differ. (For us it was /opt/virtualenv/odoo-v8/bin/odoo.py --db-filter ^%d$ -c /opt/odoo/openerp-server.conf) 

After restarting odoo with this parameter, the "view quotation" - generated link in e-mails has the installation (DB) as parameter and customer is prompted to create an account. After that ODOO succesfully can connect the dots between the quotation-customer-user, so the created user is connected to the crm customer and so forth. 

However: Atleast with our "out of the box" configuration we still have few unsolved issues:

- Customer is not automatically added to Portal - group permissions so they won't be able to view the quotations.

- Eventhough customer has already registered, any new quotations that are created will always send a new registeration token link with the e-mail as they would be new customer, instead of allowing a "returning customer with login details" to simply login and view the quotation. This might however be just a simple bug in the e-mail template.

I'm sure many other configuration issues will arise later on, if possible I'll write down more stuff as we progress to implement the module.

Hope this helps,

Erno Iipponen

Web-veistamo.fi

Anyone looking back on this issue, the problem still occurs on servers with many databases running on one server. That said there is a quick fix for this issue. I would only recommend this to people that want to export/test their project right away. 

In the openerp-server.conf file located by default at: Program Files (x86)\Odoo 8.0\server,
change the 'dbfilter' to equal the exact name of the main database you wish to use for external links. 
The final step is to restart the server, just to make sure all runs smoothly.

For example:

dbfilter = Dev_CRM

This will mean that the links default to this database, note this isn't a long term solution... Only a quick resolution. There is a clear negative of doing this, specifying a database removes the drop down from the login screen, meaning if you use multiple databases that aren't just test environments this will cause access issues.

The configuration change can always be reverted however, which will grant instant access back on the 'login page'.