Only being able to use mailgun.org without --force-ehlo

[aseques]

Hi, I am trying to use mailgun.com (they user mailgun.org for some email), and it seems that smpt-cli detects the server as SMTP only, because it's using always HELO instead of EHLO altough the server seems to be compliant

Trying to detect capabilities with telnet

$ telnet smtp.eu.mailgun.org 587
Trying 34.95.107.114...
Connected to smtp.eu.mailgun.org.
Escape character is '^]'.
220 Mailgun Influx ready
EHLO
250-4e119dd77b0c
250-AUTH PLAIN LOGIN
250-SIZE 52428800
250-8BITMIME
250-SMTPUTF8
250-PIPELINING
250 STARTTLS

./smtp-cli --server=smtp.eu.mailgun.org:587      --user=xx@example.com --pass=xxxx   --verbose  --from xx@example.com --to zzz@example.net  --subject "Simple test with attachments"              --body-plain "Log files are attached."              --attach /tmp/file.txt

[220] 'Mailgun Influx ready'
> HELO localhost
[250] '596f9cb77e29'
> MAIL FROM:<test@example.net>
[250] 'Sender address accepted'
> RCPT TO:<test@example.com>
[550] '5.7.1 Relaying denied'
RCPT TO <test@example.com> failed: '550 5.7.1 Relaying denied'
> QUIT
[221] 'See you later. Yours truly, Mailgun'

When using perl-cli with the --force-ehlo command, the emails get send without issues,

[220] 'Mailgun Influx ready'
> EHLO localhost
[250] 'bb128a7fa2d3'
[250] 'AUTH PLAIN LOGIN'
[250] 'SIZE 52428800'
[250] '8BITMIME'
[250] 'SMTPUTF8'
[250] 'PIPELINING'
[250] 'STARTTLS'
Starting TLS...
> STARTTLS
[220] 'Go ahead'
Using cipher: TLS_AES_128_GCM_SHA256
Subject Name: /C=US/ST=Texas/L=San Antonio/O=MAILGUN TECHNOLOGIES, INC/CN=*.eu.mailgun.org
Issuer  Name: /C=US/O=DigiCert Inc/CN=DigiCert TLS RSA SHA256 2020 CA1
> EHLO localhost
[250] 'bb128a7fa2d3'
[250] 'AUTH PLAIN LOGIN'
[250] 'SIZE 52428800'
[250] '8BITMIME'
[250] 'SMTPUTF8'
[250] 'PIPELINING'
AUTH method (PLAIN LOGIN): using LOGIN
> AUTH LOGIN
....

Related issue (with another domain here)