Android Question SMTP Client via IPv6

[Blueforcer]

Im using a android 7 device and the network SMTP lib to send emails with a public email server.
But there is a problem with when the client sends from an IPv6 adress:

025-10-01 09:48:22.480 rejected EHLO from [2001:a62:4f8:xxXX:8038:e2d5:9dfc:xxXX]: syntactically invalid argument(s): 2001:a62:4f8:xxXX:8038:e2d5:9dfc:xxXX

The problem is apparently that the mail client is sending an invalid SMTP EHLO command.
When using an IPv6 address instead of a hostname in the EHLO, it must be prefixed with "IPv6:" (see RFC 2821, section 4.1.3 Address Literals).

 

[Erel]

Please try the attached library - v1.82.

 

[Blueforcer]

It is still being rejected.

 

[Erel]

Can you post the logs?

 

[Blueforcer]

Unfortunately not, I got the information from the provider's service hotline. I have to ask if they “have time” to debug with me. But I suspect they won't do that.
im using variomedia.de

 

[Erel]

What do you see in the app logs?

 

[Blueforcer]

I only get

503 STARTTLS command used when not advertised.

But of course that happens because the email server already blocks it beforehand.

 

[Erel]

Try this one. You should see a message in the logs, starting with ehlo.

 

[Blueforcer]

Try this one. You should see a message in the logs, starting with ehlo.

With this version it works! email was sent
ehlo: [IPv6:2a02:8071:5cb1:59xx:1a1:3a21:3fdc:1XXX]