Question Can't access to Mail "Conntection to fileserver failed" (Outlook & Roundcube)

[Lukas_Multi]

Hey,

i'm trying to setup a connection from Microsoft Outlook to a Plesk-generated Mail account. It isn't working.
I tried:

• Login via Roundcube. (Error: "Verbindung zum Speicherserver fehlgeschlagen."
• Login via Ms Outlook. Dosen't work with IMAP (Ports 933, 143) or POP
• Login via Mozilla Thunderbird. The Settings of the Server are found but if i click "Finish", an Error (Login to server faild. Maybe the Configuration, Username oder Password are incorrect.) happens. I am 100% sure that the Username and Password are correct.
• Re-Installed the complete Domain to see if it works after. Didn't helped.

Maybe someone knows a solution!
Thanks a lot!

My System:
Plesk Obsidian Web Admin Edition - Version 18.0.19
Linux Ubuntu 20.4
Hosted by webtropia.com

 

[Bitpalast]

The error occurs when the number of concurrent connections to Dovecot exceeds the limit. You need to edit two files to be sure that it will always work:

Create a file /etc/dovecot/conf.d/99-imap-login.conf with this content:

service imap-login {
process_limit = 2000
process_min_avail = 16
}

Adapt process_limit and process_min_avail to your needs. The values above are generous and will most likely fit. They might be too high if you wish to protect your server from a lot of useless logins.

Create an additional config file /etc/dovecot/conf.d/10-master.conf with this content:

default_client_limit = 5000

or another very high number that is always higher than the maximum number of concurrent clients. Many clients create at least four IMAP connections, so if you are hosting 100 mailboxes and users are using IMAP, you will want to consider to set the value to at least 400, else some customers might not be able to log in if the server is under heavy load. On the other hand, do not set the value too high, because again, you open a door for a similar-to-ddos-attack when you allow too many useless connections.

After these changes, restart Dovecot, e.g.

# service dovecot restart

 

[Lukas_Multi]

I Created "10-master.conf" at "/etc/dovecot/conf.d":

default_client_limit = 5000

And i created "99-imap-login.conf" at "/etc/dovecot/conf.d":

service imap-login{
process_limit = 2000
process_min_avail = 16
}

I restarted the Service and it is still not working..
Do you maybe need some Logs? (if yes, tell me wich one)

 

[Bitpalast]

Any more data in the /var/log/maillog file on this? Is your SMTP server up, too?

 

[Lukas_Multi]

In the maillog file i can only find Connecting fails from Lithuania.
Here is the last 30min:

Expand/Collapse Block: Maillog

Feb  5 13:33:04 vps2048339 plesk_saslauthd[32097]: failed mail authentication attempt for user 'metro' (password len=7)
Feb  5 13:33:04 vps2048339 postfix/smtpd[32094]: warning: unknown[141.98.10.143]: SASL LOGIN authentication failed: authentication failure
Feb  5 13:33:04 vps2048339 postfix/smtpd[32094]: disconnect from unknown[141.98.10.143] ehlo=1 auth=0/1 quit=1 commands=2/3
Feb  5 13:33:34 vps2048339 plesk_saslauthd[32097]: select timeout, exiting
Feb  5 13:36:24 vps2048339 postfix/anvil[32096]: statistics: max connection rate 1/60s for (smtp:141.98.10.143) at Feb  5 13:33:03
Feb  5 13:36:24 vps2048339 postfix/anvil[32096]: statistics: max connection count 1 for (smtp:141.98.10.143) at Feb  5 13:33:03
Feb  5 13:36:24 vps2048339 postfix/anvil[32096]: statistics: max cache size 1 at Feb  5 13:33:03
Feb  5 13:55:31 vps2048339 postfix/smtpd[33838]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled
Feb  5 13:55:32 vps2048339 postfix/smtpd[33838]: connect from unknown[18.205.72.90]
Feb  5 13:55:33 vps2048339 postfix/smtpd[33838]: NOQUEUE: reject: RCPT from unknown[18.205.72.90]: 554 5.7.1 <test@mxtoolboxsmtpdiag.com>: Relay access denied; from=<supertool@mxtoolboxsmtpdiag.com> to=<test@mxtoolboxsmtpdiag.com> proto>
Feb  5 13:55:33 vps2048339 postfix/smtpd[33838]: disconnect from unknown[18.205.72.90] ehlo=1 mail=1 rcpt=0/1 quit=1 commands=3/4
Feb  5 13:55:33 vps2048339 psa-pc-remote[7863]: Message aborted.
Feb  5 13:55:33 vps2048339 psa-pc-remote[7863]: Message aborted.
Feb  5 13:57:23 vps2048339 postfix/smtpd[34002]: warning: dict_nis_init: NIS domain name not set - NIS lookups disabled
Feb  5 13:57:23 vps2048339 postfix/smtpd[34002]: connect from mone183.secundiarourous.com[141.98.10.183]
Feb  5 13:57:23 vps2048339 plesk_saslauthd[34004]: listen=6, status=5, dbpath='/plesk/passwd.db', keypath='/plesk/passwd_db_key', chroot=1, unprivileged=1
Feb  5 13:57:23 vps2048339 plesk_saslauthd[34004]: privileges set to (111:116) (effective 111:116)
Feb  5 13:57:23 vps2048339 plesk_saslauthd[34004]: failed mail authentication attempt for user 'tech' (password len=6)
Feb  5 13:57:23 vps2048339 postfix/smtpd[34002]: warning: mone183.secundiarourous.com[141.98.10.183]: SASL LOGIN authentication failed: authentication failure
Feb  5 13:57:23 vps2048339 postfix/smtpd[34002]: disconnect from mone183.secundiarourous.com[141.98.10.183] ehlo=1 auth=0/1 quit=1 commands=2/3
Feb  5 13:57:53 vps2048339 plesk_saslauthd[34004]: select timeout, exiting
Feb  5 13:58:15 vps2048339 postfix/smtpd[34002]: connect from unknown[141.98.10.136]
Feb  5 13:58:15 vps2048339 plesk_saslauthd[34089]: listen=6, status=5, dbpath='/plesk/passwd.db', keypath='/plesk/passwd_db_key', chroot=1, unprivileged=1
Feb  5 13:58:15 vps2048339 plesk_saslauthd[34089]: privileges set to (111:116) (effective 111:116)
Feb  5 13:58:15 vps2048339 plesk_saslauthd[34089]: failed mail authentication attempt for user 'alerts' (password len=8)
Feb  5 13:58:15 vps2048339 postfix/smtpd[34002]: warning: unknown[141.98.10.136]: SASL LOGIN authentication failed: authentication failure
Feb  5 13:58:15 vps2048339 postfix/smtpd[34002]: disconnect from unknown[141.98.10.136] ehlo=1 auth=0/1 quit=1 commands=2/3

The SMTP seems to be online (checked it wit MX-Toolbox):

 

[Bitpalast]

I think there are at least two different issues here.

One is that the local webmail client cannot connect to the local mail storage server. The error message "Verbindung zum Speicherserver fehlgeschlagen." either means that the service is not running that the capacity for logins has been exceeded or that the port cannot be accessed.

The other issue is that you cannot connect from your external mail client to the server.

Given all the information in this thread I suggest to verify that your local server IP and your remote DSL client IP are not blocked by Fail2Ban. Both, 127.0.0.1, and your server's own IPv4 address should be on the whitelist in Tools & Settings > Security > Fail2Ban.

 

[Lukas_Multi]

Both IP's are on the Trusted List.
Is it maybe the Same problem for an extrenal Mail-Client as for the Web-Client?

I tested it again with Mozilla Thunderbird, still not working.
In the end the most important thing would be that i can use the mailserver in Outlook.

 

[Bitpalast]

In your maillog there is no indication that a login attempt is made from your Outlook, nor from your webmail application. This only leaves one conclusion, that the mail ports are inaccessible or that no mail service is running on them.

Your maillog does not show anything from Dovecot, which is unusual. You wrote in your earlier post that you have restarted Dovecot, but are your really sure that it is running?
# service dovecot status

If Dovecot is running on these, you should see it and also get a green status from the status command. In that case, as you cannot connect to the service, the only conclusion left would be that the ports are blocked. The information does not match, you must be overlooking something. Can you please check what is going on on your ports 143 and 993? For example using
# lsof -i:143
# lsof -i:993