callstack.md

src/dc_smtp.c:180

mailsmtp_auth() returns MAILSMTP_ERROR_AUTH_LOGIN

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libs/libetpan/src/low-level/smtp/mailsmtp.c:1060

returns result from mailsmtp_auth_type()

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libs/libetpan/src/low-level/smtp/mailsmtp.c:1032

returns result from mailsmtp_auth_sasl()

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libs/libetpan/src/low-level/smtp/mailsmtp.c:1379

this is where MAILSMTP_ERROR_AUTH_LOGIN is returned from, which is due to sasl_client_start() failing, which returns status -4, which according to libs/cyrussasl/include/sasl/sasl.h corresponds to SASL_NOMECH (mechanism not supported)

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core-smtp-from-inside-docker.md

When connecting from "normal" environment into greenmail I see the following smtp traffic:

220 /172.17.0.2 GreenMail SMTP Service v1.5.8 ready
EHLO x240
250-/172.17.0.2
250 AUTH PLAIN
AUTH PLAIN ZGVsdGExAGRlbHRhMQBkZWx0YTE=
235 2.7.0  Authentication Succeeded
QUIT
221 /172.17.0.2 Service closing transmission channel

When connecting from the inside of a docker container I see the following smtp traffic:

220 /172.17.0.2 GreenMail SMTP Service v1.5.8 ready
EHLO 017e4c835007
250-/172.17.0.2
250 AUTH PLAIN
QUIT
221 /172.17.0.2 Service closing transmission channel

In the docker case, we can see that the client doesn't send AUTH PLAIN ZGVsdGExAGRlbHRhMQBkZWx0YTE= back. So it's possible that something goes wrong before this, so we don't reach that point in the code. Will throw in some printf and see if we can get more information.