The above solution did not work for me in my oddo11 vanilla installaiton.
Problem was that incomming emails for my two users where not routed to the odoo inbox at all.
Now I found an aliase configuration that worked.

info            Lead/Opportunity    John Doe           {'type': 'lead', 'team_id': 4}                 Everyone
sales           Lead/Opportunity                              {'type': 'opportunity', 'team_id': 1}    Everyone
discover     Task                                                      {'project_id': 1}                                     Everyone
admin        Users                        Administrator   {'user_id':1}                                           Everyone
john            Users                       John Doe            {'user_id':5}                                           Everyone

What did the trick was using alias model 'Users' and {'user_id':5} as Default Value along with the correct user_id of the user.

Same with incoming mails for leads.

Using the alias model 'eMail Thread' (it was suggested somewhere else) just ignored the mail completely.
It was marked as read in the imap folder but did not appear at all in odoos message list.

Though the above solved my actual problem and may proove helpfull for others, my main question still remains:
Where can I find a usefull documentation how these alias models are configured correctly and what they do if done so...

Cheers
Stephan

Hello Team 

I am using Odoo 13. And i tried setting up the email system. I am able to send emails through Odoo. However i can not receive emails in Odoo. 

Any help please. 

Thanks

Rishal Chand

where is this  Record Thread ID and  Parent Record Thread ID in each user?

Example for odoo 8

When you activate in settings>configuration>project an option to "create issues from an incoming email account" (also you need an email account configured in setting>technical>email>incoming mail server) you will have an alias option for projects and users. Just cpecify new alias in user or project settings and odoo will automatically create it in settings>technical>email>aliases.

If you can't setup catchall mailbox, you may leave default value for settings>configuration>general>email>alias domain. When somebody would write a letter for user or project with virtual email (alias), it doesn't matter which mail server may be specified. Just specify two recipients 1)odoo incoming mailbox, 2)  user_alias@anymailbox.com. Odoo will recieve email, and if it see in recipients user_alias, it will redirect it to user's "messaging>inbox". Same for project alias.