recipient address rejected / smtp error 550 5.7.1

[supervisitor]

I got error message with reason: helo/hostname mismatch. I was looking to the logs and found the MTA helo: "android.com", which is wrong in any case. Best way should be the name of IP.

[grote]

While the helo is not optimal, I don't think it is related to your problem. Which port are you using? Usually this error indicates you are using unauthenticated login on port 25.

[supervisitor]

I do not want to persuade or respeak to you. But I have tested it and assigned "android.com" in DNS the IP I use. Then it worked. After deleting this record from DNS, the error message is back and I'm no more able to send messages. ;o) Sorry...

In the office I use a universal mail proxy solution at local WLAN. This is able to work with or without SSL and with or without authentication. It accepts connections on port 24, 25, 58, 143, 158, 209, 366, 465, 587, 2041, 2095, 2096, 2525, 3535, 4069, 4443, 5108, 5109, 7025, 10024, 10025, 24554 (list of ports from pf.conf for sending mail). This machine is full transparent, but pre-checks some casualness of design. - And in the meantime I check this via WAN without a proxy, in this configuration I get the same error from my provider MTA (port 465).