Question Couldn't open connection to server - IMAP - Samsung Android Mail

[avlza]

I am trying to setup my email hosted on Plesk via VULTR on my Android Phone and I get the error Couldn't open connection to server.

I did a manual setup with the following settings :

Mail server username : My Email Address
Incoming mail server : My Domain Address (example.com)
Outgoing mail server : My Domain Address (example.com) (server requires authentication)

IMAP securely over SSL/TLS : port 993.
SMTP : port 465.

But still, no-go.


I tried following this article, still I get the same error.

 

[IgorG]

Make sure that ports 993 (IMAP) and 465 (SMTP) is listening on your Plesk server, not firewalled and accessible from your Android phone.

 

[avlza]

Make sure that ports 993 (IMAP) and 465 (SMTP) is listening on your Plesk server, not firewalled and accessible from your Android phone.

Thanks for your advice, but how do I check the if the ports are listening to my server?

 

[Kaspar]

See: How To Manually Test Connectivity To IMAP/POP/SMTP Services | ServerGuy.com

 

[Bitpalast]

Some e-mail applications have difficulties with proper authentication with DIGEST-MD5, e.g. Android Mail App. What they do is to always first try DIGEST-MD5 als encryption algorithm, which fails because what the server returns cannot be interpreted by the phone correctly and what the phone sends cannot be understood by the server correctly (for unknown reason). This causes two auth failure entries in the maillog file. When you have Fail2Ban enabled, these two auth failures trigger the jail so that the IP address that the phone is using will be blocked. This again leads to your symptom that your phone cannot connect to the server.

For that reason, remove this mechanism from Dovecot. The apps will then automatically use another mechanism.

# vi /etc/dovecot/conf.d/00-auth_mechs.conf

auth_mechanisms = plain login cram-md5 apop

# vi /etc/dovecot/dovecot.conf
and remove “digest-md5” from auth_mechanisms line.

Then restart Dovecot
# service dovecot restart

Then unblock the IP address of your phone (go to a website like whatismyipaddress.com on your phone, read the IPv4/IPv6 address and unblock it in Plesk Fail2Ban.