SMTP API Error - ErrorCode: '300', Message: 'Zero-sized attachments not allowed.'.

[irrweg]

Bug report

Steps to reproduce

1. Attache a file to the Mail you going to send.
2. Now you get a 0KB file as attachment.
3. Send the E-Mail.

Expected behavior

The attachment which is still their causes some problems on the SMTP side.

Actual behavior

E-Mail gets rejected without any information that it was rejected.
The reason for it was Zero-sized attachment.

After I removed the attachment, it worked fine.

This is a Screenshot from Postmark.

Server configuration

Operating system:

Debian 9

Web server:

Ngnix

Database:

MySQL

PHP version:

7

Nextcloud version:

15

Updated from an older installation or fresh install:

Fresh

The content of config/config.php:

' ', 'secret' => ' ', 'trusted_domains' => array ( 0 => 'localhost', 1 => ' ', ), 'datadirectory' => '/web/nextcloud/data', 'dbtype' => 'mysql', 'version' => '15.0.5.3', 'overwrite.cli.url' => 'http://localhost', 'dbname' => ' ', 'dbhost' => 'mysql', 'dbport' => '', 'dbtableprefix' => 'nc_', 'mysql.utf8mb4' => true, 'dbuser' => ' ', 'dbpassword' => ' ', 'installed' => true, 'instanceid' => ' ', 'redis' => array ( 'host' => 'redis', 'port' => 6379, 'timeout' => 0, 'dbindex' => 10, ), 'memcache.locking' => '\\OC\\Memcache\\Redis', 'memcache.local' => '\\OC\\Memcache\\Redis', 'trusted_proxies' => array ( 0 => ' ', 1 => ' ', ), 'overwritewebroot' => '/', 'overwritehost' => ' ', 'overwriteprotocol' => 'https', 'mail_smtpmode' => 'smtp', 'mail_smtpauthtype' => 'LOGIN', 'mail_from_address' => 'catchme', 'mail_domain' => ' ', 'mail_smtphost' => 'smtp.postmarkapp.com', 'mail_smtpport' => '587', 'user_backends' => array ( 0 => array ( 'arguments' => array ( 0 => '{dovecot:143/imap/tls/novalidate-cert}', ), 'class' => 'OC_User_IMAP', ), ), 'mail_sendmailmode' => 'smtp', 'mail_smtpsecure' => 'tls', 'mail_smtpauth' => 1, 'mail_smtpname' => ' ', 'mail_smtppassword' => ' ', 'trashbin_retention_obligation' => 'auto', 'versions_retention_obligation' => 'auto', 'logfile' => '/var/log/nextcloud.log', 'preview_max_filesize_image' => 150, 'max_filesize_animated_gifs_public_sharing' => -1, 'allow_user_to_change_display_name' => true, );

Are you using external storage, if yes which one: local folder, smb share, sftp, etc.

No.

Are you using encryption: yes/no

No.

Desktop configuration

Operating system:

Win10

Thunderbird version:

60.5.3