Bugs und improvement suggestions for GMX

I've got an account for Global Mail Exchange. It has repeatedly caused me problems, which in my opinion come from deficiencies in their server implementation. Most of these problems haven't been resolved to date.

Wrong > character in lines starting with from

Mails that were received via GMX get a > character appended to all lines that start in from, regardles of case. This is irritating while you read it, and can invalidate digital signatures. There are storage formats that require lines beginning with From  in exactly this spelling to be escaped, but this is for storage only and should be undone when a message is passed on.

The problem was filed as ID[|#1695324880#5134788#5bc0175#|] at GMX. Later I got a mail with the new ID[|#1695324880#5272077#5b6016f#|], stating that for some problem no technical solution was possible. From the timing of this message I have to assume they referred to the issue described here, although enquiris to this effect remained unanswered.

SMTP: ESMTPA label to better distinguish from spam

Spam filters like SpamAssassin try to find out from where a mail was sent, and treat mails from dynamic dial-up addresses more likely as spam than mails from known legitimate mail servers. Mails from authorized GMX customers should in this sense be treated as originating from the GMX server. The fact that a user had authenticated is noted in a header called X-Authenticated, but this is easy to fake and ignored altogether by SpamAssassin.

SpamAssassin, on the other hand, looks in detail at the Received heraders. If one of these contains with ESMTPA (Extended Simple Mail Transfer Protocol Authenticated), that host will be held rsponsible for the mail, and dial-up IPs on the way to this host will become irrelevant. Sadly, GMX tags its mail only as with SMTP.

One would assume that adding two letters to a string shouldn't be too difficult, and that the servers would know whether or nor they are dealing with an authenticated user. The issue was forwarded to Tech Support according to ID[|#1695324880#4311007#5850161#|], and rejected in ID[|#1695324880#4468943#5df0177#|] due to the fact that the SpamAssassin installations rejecting the GMX mails due to this issue here were not the SpamAssassin maintained by GMX itself.

SMTP: State failing address in 5.1.2 error messages

When you send a mail to a larger number of recipients, and one of these addresses contains a wrong domain naime, GMX will send an error message like this: 550 5.1.2 Cannot resolve your domain. Either your mail user agent will tell you for which address it received that error message, or it's up to you to check or try them one by one. In the similar case of an invaliud recipient name with a GMX address, the error message sent by GMX will contain the address causing this error.

The problem was filed as ID[|#1695324880#6391657#5d70176#|]. I received two mails supposedly on this issue, which both had nothing at all to do with my request. Instead I fixed the issue for my favorite MUA, Mozilla Thunderbird.

POP3: Connection terminated on failed authentication (resolved)

After entering a wrong passwort using the AUTH command, and trying again with the legacy USER command, the server used to terminate the connection upon receipt of the USER command, instead of asking for a password and sending an error message if that was incorrect as well. Incombination with a bug in Thunderbird this could cause failure without any error message when the password was wrong.

This issue has been resolved by GMX, and they even thanked me for the precise error description.