IMAP error "Creating account failed: Could not connect to IMAP: Error connecting to mail server."

[fds2610]

Expected behavior

want to add an imap account to mail app

Actual behavior

does not create account

Mail app

1.3.2

Strato: imap.strato.de:993

Server configuration

Ubuntu 18.04

Apache

MySQL

php 7.3

NC 18.0.3

Client configuration

FF 75

Win10

I can access the imap-server from my thunderbird client using exact same credentials and data.
provider tells me they support only thunderbird, outlook, ios and android.

nextcloud-log says:

{"reqId":"CMBZbC19hqBNRpA7daHN","level":0,"time":"2020-04-21T15:08:41+00:00","remoteAddr":"192.168.2.43","user":"fs@dsd","app":"PHP","method":"POST","url":"/index.php/apps/mail/api/accounts","message":"stream_socket_client(): unable to connect to ssl://imap.strato.de:993 (Connection timed out) at /var/www/nextcloud/apps/mail/vendor/pear-pear.horde.org/Horde_Socket_Client/Horde/Socket/Client.php#293","userAgent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0","version":"18.0.3.0"}
{"reqId":"CMBZbC19hqBNRpA7daHN","level":4,"time":"2020-04-21T15:08:41+00:00","remoteAddr":"192.168.2.43","user":"xxxxxxx","app":"mail","method":"POST","url":"/index.php/apps/mail/api/accounts","message":"Creating account failed: Could not connect to IMAP: Error connecting to mail server.","userAgent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0","version":"18.0.3.0"}

horde-imap-log:

Tue, 21 Apr 2020 15:05:18 +0000
Connection to: imap://imap.strato.de:993/
Slow Command: 20.02 seconds
Connection failed: Error connecting to server.

[ChristophWurst]

(Connection timed out)

Is the mail host reachable from the nextcloud host? Did you use the correct port?

[fds2610]

Hi @ChristophWurst , well.
IPv4 works fine, but IPv6 times out...
$ ping -4 imap.strato.de
PING imap.strato.de (81.169.145.103) 56(84) bytes of data.
64 bytes from imap.strato.de (81.169.145.103): icmp_seq=1 ttl=246 time=20.7 ms

How can i make mail use IPv4 ?

ok, if i disable IPv6 on the main (internet) interface by OS, mail can connect to the imap server. maybe it could be a feature-request to add an option to "manual settings" to use IPv4 / IPv6 or both.

so, please remove my "bug" label and add "feature-request" or "enhancement".

[ChristophWurst]

How can i make mail use IPv4 ?

Use the IP.

If your host name resolves to an ipv4 and an ipv6 but just one of the two is usable then I would say your network setup is invalid.

[fds2610]

Hello Christoph, thanks for your review of this question. As this is more a networking / operatingsystem issue instead of a nextcloud topic I will close it now.
BTW: using the IP address is worse than disabling unused IPv6 in the OS, because many mail provider change their IP addresses without notice. That is the reason for using DNS. I assume you know all of this, but i write it doen in case future users encounter similar problems. thanx again !