[FIX] mail: 17.0 full rework of mail communication documentation

1/ Revamp of email_servers to be a introduction and allow correct redirection
+ redirection to other pages linked to mailing + ToC of email_communication folder

2/ Splitting inbound and outbound message into subfiles:
2.a/ email_servers_inbound: all documentation related to incoming emails
2.b/ email_servers_outbound: documentartion related to outgoing emails

3/ email_domain (as before) about authentication protocols to set on domains.

4/ faq: complete revamp to better match usual issues about mailings.

Also: removed unused images, adding anchors on other docs.

RST co-authored-by: jorv-odoo, jqu-odoo, xpl-odoo

doc writers:
- email_servers_inbound by qco-odoo
- email_servers_outbound by EMBR
- email_servers by abridbus
- email_domain by jqu-odoo
- faq by jorv-odoo

related documentation task-3875591

closes odoo/documentation#10582

X-original-commit: 00077597d2
Signed-off-by: Xavier Platteau (xpl) <xpl@odoo.com>

content/applications/sales/crm/acquire_leads/email_manual.rst

@@ -13,6 +13,8 @@ First, ensure the *Leads* feature is enabled in the database by navigating to :m
 app --> Configuration --> Settings`. Tick the :guilabel:`Leads` checkbox, then click
 :guilabel:`Save`.
 
+.. _crm/configure_email_alias:
+
 Configure email aliases
 =======================
 
@@ -58,7 +60,7 @@ contact's email address.
    to the database as opportunities.
 
 .. seealso::
-   :doc:`../../../general/email_communication/email_servers`
+   :doc:`../../../general/email_communication`
 
 Manually create leads
 =====================