Maillog entries:
May 20 15:22:31 mustang sendmail[132997]: 64K5qVnk132997: AUTH failure (LOGIN): generic failure (-1) SASL(-1): generic failure: checkpass failed, user=scldad, relay=localhost [127.0.0.1]
May 20 15:22:31 mustang sendmail[132997]: 64K5qVnk132997: localhost [127.0.0.1] did not issue MAIL/EXPN/VRFY/ETRN during connection to MSA
May 20 15:23:45 mustang dovecot[2234]: imap-login: Login: user=<scldad>, method=PLAIN, rip=219.93.12.138, lip=203.2.199.4, mpid=133035, TLS, session=<cs8pazlSiLfbXQyK>
May 20 15:23:46 mustang sendmail[133060]: 64K5rkVp133060: AUTH failure (LOGIN): generic failure (-1) SASL(-1): generic failure: checkpass failed, user=scldad, relay=localhost [127.0.0.1]
May 20 15:23:46 mustang sendmail[133060]: 64K5rkVp133060: localhost [127.0.0.1] did not issue MAIL/EXPN/VRFY/ETRN during connection to MSA
May 20 15:23:47 mustang dovecot[2234]: imap-login: Login: user=<scldad>, method=PLAIN, rip=219.93.12.138, lip=203.2.199.4, mpid=133096, TLS, session=<IEVUazlSirfbXQyK>

For a Gmail style preview experience the Chrome extension Docs Online Viewer is probably the closest match

There really isn't much information to go off of there without knowing what the device is getting or the server is sending there isn't anything to go off of.

Unfortunately, Android browsers do not have (or I cannot find) a debug- facility where I can network traffic.
Here are the HTTP log entries:

219.93.12.138 - - [20/May/2026:10:13:51 +0930] "GET /roundcubemail/?_task=mail&_action=compose&_id=2885358406a0d02a429162 HTTP/1.1" 200 34475 "http://www.sdc.com.au/roundcubemail/?_task=mail&_mbox=INBOX" "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/148.0.0.0 Safari/537.36"
219.93.12.138 - - [20/May/2026:10:13:58 +0930] "POST /roundcubemail/?_task=mail&_action=autocomplete HTTP/1.1" 200 93 "http://www.sdc.com.au/roundcubemail/?_task=mail&_action=compose&_id=2885358406a0d02a429162" "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/148.0.0.0 Safari/537.36"
219.93.12.138 - - [20/May/2026:10:14:01 +0930] "POST /roundcubemail/?_task=mail&_action=autocomplete HTTP/1.1" 200 94 "http://www.sdc.com.au/roundcubemail/?_task=mail&_action=compose&_id=2885358406a0d02a429162" "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/148.0.0.0 Safari/537.36"
219.93.12.138 - - [20/May/2026:10:14:18 +0930] "POST /roundcubemail/?_task=mail&_unlock=loading1779237857109&_framed=1 HTTP/1.1" 200 398 "http://www.sdc.com.au/roundcubemail/?_task=mail&_action=compose&_id=2885358406a0d02a429162" "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/148.0.0.0 Safari/537.36"
219.93.12.138 - - [20/May/2026:10:16:06 +0930] "GET /roundcubemail/?_task=mail&_action=compose&_id=2885358406a0d02a429162 HTTP/1.1" 200 34475 "http://www.sdc.com.au/roundcubemail/?_task=mail&_mbox=INBOX" "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/148.0.0.0 Safari/537.36"

What response code is the browser receiving and can you very what the server is sending?

This is probably something that need to be fixed in Roundcube core. Seems asset_url() should be made available for ajax requests too. But it might not be an easy fix.

ps. Larry skin uses optionsmenuIcon="true" and I don't see any issues.

ok ... I've removed both occurances of optionsmenuIcon="true" - but the errors still get coming in :-/

[19-May-2026 07:26:44 UTC] PHP Fatal error:  Uncaught Error: Call to undefined method rcmail_output_json::asset_url() in /var/www/vhosts/futuremail.at/httpdocs/program/actions/mail/index.php:740
[19-May-2026 07:27:27 UTC] PHP Fatal error:  Uncaught Error: Call to undefined method rcmail_output_json::asset_url() in /var/www/vhosts/futuremail.at/httpdocs/program/actions/mail/index.php:740
[19-May-2026 07:28:32 UTC] PHP Fatal error:  Uncaught Error: Call to undefined method rcmail_output_json::asset_url() in /var/www/vhosts/futuremail.at/httpdocs/program/actions/mail/index.php:740


I have been using roundcubemail for nine years and have happily accessed my mail server from all over the world.
However, I am now in Penang and can download incoming emails without issue but any attempt to send email gives an authorisation error.
I have tried connecting via my hotel WiFi and via mobile phone. No difference.
Nothing has changed at my server and nothing apart from location has changed on my Android devices  (three thereof).

PHP Error. Invalid response code from server.
Version 1.6.15. Rocky Linux server. Android clients.

HELP!!

Using only "From does not contain Re" usually will not work properly because "Re" is normally in the subject line not the sender address a better approach would be Condition Subject does not contain "Re"AND set the autoresponder to reply only once per sender/thread within a certain time period. Some mail systems also have options like.

"Send vacation reply once per sender" "Do not reply to auto-submitted emails" "Ignore duplicate subjects/tickets"

If your system supports ticket IDs or threading that is the best method to avoid repeated auto-replies for the same issue.

I decided to look into this and I found the root cause. When you click on the drop down the onclick function calls "d.load(location.href + ' #identity_switch_dropdown > *', '');". In Roundcube 1.6.x calling location.href would return the html for the current page but inn 1.7.x it returns a json object. This is causing jQuery to clear the div since #identity_switch_dropdown doesn't exist in the json returned by the load call.

A quick fix is just to remove that line but if the data refresh is needed it should be replaced with a plugin specific route to fetch the data needed.