(Dutch) advanced facilities for email:
https://www.startmail.com
https://soverin.net
https://mailfence.com
https://freedom.nl (started up)

Free Outlook app for Android mobile phone:
Just enter the email address as username plus the password.
Server settings can be set automatically.

How to setup eg Outlook (for a mailbox of a web domain):

• Connection protocol IMAP is often more suitable than POP3, which removes mail from the mailbox;
• The mail server of an ISP (Internet Service Provider) is actually only properly authorized with the mail address of that ISP;
• The domain of an organization is usually suitable such as mail.sitedomain.com;
• A missing SSL certificate for a pop / imap / smtp subdomain may block. I do let Outlook default ‘mail’;
• If mail.sitedomain.com is the mail server or a mail service that is not known for high numbers, it may be better to authorize in SPF for the domain of the ISP, and use the mail server of the ISP;
• Using mobile: Providers may not connect to other mail servers then their own;
• Fill user name including the @… part;
• Tick: save password;
• Tick: use same password for outbound mail;
• Incoming encryption SSL / automatic, port 993 (using IMAP);
• Outbound encryption TLS / automatic, port 587 (or port 465);

Testing facilities:
https://internet.nl (publicly accessible testresult):

Allow IPv6 with MX mail server (s)
Secure DNS of MX mail server (s)
Validity for outbound from these mail service types:
– the server itself, or relay, with or without SRS, in MTA configuration
– SMTP mail service (common setting in a high-volume application)
– HTTP mail service (works with a library in order to communicate with the mail server)
– MX mail server (to bounce an incoming email)
Sniffer Proof of MX mail server (s)

https://mecsa.jrc.ec.europa.eu (private accessible state-of-the-art test result and explanation)
https://www.dmarctester.com (private accessible test result)
https://mail-tester.com (private accessible proven test result)
http://dkimvalidator.com
https://kitterman.com/spf/validate.html
https://toolbox.googleapps.com

Check on dmarc=fail:
– In delivered email source in webmail at your internet provider.
– DMARC with “p=quarantine” stores email in spam in case of a non-legitimate mail server.

How to open port 587 in control panel Plesk:
– Outlook with SSL on port 465 does work also with TLS on port 587;
– Removed ‘#’ from /etc/postfix/master.cf before: submission inet n – n – – smtpd and restarted Postfix: # systemctl restart postfix.service;
– Plesk also has a formfield for port 587 in mail server setup to change to yes.