Error when sending email to gmx.de

[mworrell]

When sending an email to gmx.de addresses I get the following error:

2024-05-30 16:53:08 INFO  site=xxxxx  user_id=1 <0.2227423.0> [z_email_server:send_blocking_smtp/6:1100] ▸ message_id=olybuaxut0jyaoasdnqu recipient=redacted@gmx.de relay=gmx.de text="Sending email" port=undefined in=zotonic_core
2024-05-30 16:53:09 ERROR <0.2227423.0> [:] ▸ text="Error in process <0.2227423.0> on node zotonic@consult with exit value:\
{{case_clause,<<0>>},\
 [{gen_smtp_client,read_possible_multiline_reply,1,\
                   [{file,\"/home/zotonic/zotonic/_build/default/lib/gen_smtp/src/gen_smtp_client.erl\"},\
                    {line,841}]},\
  {gen_smtp_client,try_MAIL_FROM,4,\
                   [{file,\"/home/zotonic/zotonic/_build/default/lib/gen_smtp/src/gen_smtp_client.erl\"},\
                    {line,416}]},\
  {gen_smtp_client,try_sending_it,4,\
                   [{file,\"/home/zotonic/zotonic/_build/default/lib/gen_smtp/src/gen_smtp_client.erl\"},\
                    {line,400}]},\
  {gen_smtp_client,send_it,2,\
                   [{file,\"/home/zotonic/zotonic/_build/default/lib/gen_smtp/src/gen_smtp_client.erl\"},\
                    {line,300}]},\
  {z_email_server,send_blocking_smtp,6,\
                  [{file,\"/home/zotonic/zotonic/_build/default/lib/zotonic_core/src/smtp/z_email_server.erl\"},\
                   {line,1109}]},\
  {z_email_server,spawned_email_sender_loop,13,\
                  [{file,\"/home/zotonic/zotonic/_build/default/lib/zotonic_core/src/smtp/z_email_server.erl\"},\
                   {line,946}]}]}\

Notes:

• This is when sending the email using TLS