When you check the mail log you see and error like this:
Mar 3 03:46:41 server amavis[1760673]: (1760673-07) (!)WARN save_info_final: sql exec: err=1366, 22007, DBD::MariaDB::st execute failed: Incorrect string value: '\\xF0\\x9F\\x98\\x8E\\xF0\\x9F...' for column `dana
mi_warden`.`msgs`.`subject` at row 1 at /usr/share/perl5/vendor_perl/Amavis/Out/SQL/Connection.pm line 175, <GEN124> line 1923.This is because the mail subject contains an emojis or rare character not supported by the current danami_warden database character set. Administrators can fix this error by following the instructions from the KB article below to convert their database from utf8mb3 to utf8mb4 which supports the full Unicode standard, including emojis and rare characters (If supported by your database version):
How can I convert the Warden database to use the character set utf8mb4 instead of utf8mb3?
