I have this same type problem. I believe I have my account set up correctly, and have an SMTP Log which shows what the failure is. If I can manage to insert it, I will. Happy day: lots of room taken up, but a short clip from the log. Note that after connecting, he reads the first message (220) which tells him some info about my ISP's server. Then he writes an EHLO to the server. He reads the next message from the server, and gets message (250) which tells him more about the server characteristics I think. But then, he writes and EHLO again, and bang, he reads the next message, which is
503: Saw HELO/EHLO already. That is quitting time, and he is now OFFLINE.
Now, I left my work with IBM about 10 years ago, am 81 yrs old, and I have not had to debug any Apple code over the years, so I need to know if I can still access the Apple Knowledge Base info, how I might talk to a developer or tech guru, or if anything else that I could do to technical help.
CONNECTED Oct 20 16:40:48.124 [kCFStreamSocketSecurityLevelNone] -- host:smtp.everyone.net -- port:25 -- socket:0x6000004bbc00 -- thread:0x60800107e4c0
READ Oct 20 16:40:48.164 [kCFStreamSocketSecurityLevelNone] -- host:smtp.everyone.net -- port:25 -- socket:0x6000004bbc00 -- thread:0x60800107e4c0
220 dm0201.mta.everyone.net ESMTP EON-AUTHRELAY2
WROTE Oct 20 16:40:48.461 [kCFStreamSocketSecurityLevelNone] -- host:smtp.everyone.net -- port:25 -- socket:0x6000004bbc00 -- thread:0x60800107e4c0
EHLO [10.0.1.6]
READ Oct 20 16:40:48.515 [kCFStreamSocketSecurityLevelNone] -- host:smtp.everyone.net -- port:25 -- socket:0x6000004bbc00 -- thread:0x60800107e4c0
250-dm0201.mta.everyone.net
250-PIPELINING
250-SIZE 50000000
250-AUTH PLAIN LOGIN
250-AUTH=LOGIN
250 8BITMIME
WROTE Oct 20 16:40:48.515 [kCFStreamSocketSecurityLevelNone] -- host:smtp.everyone.net -- port:25 -- socket:0x6000004bbc00 -- thread:0x60800107e4c0
EHLO [10.0.1.6]
READ Oct 20 16:40:48.567 [kCFStreamSocketSecurityLevelNone] -- host:smtp.everyone.net -- port:25 -- socket:0x6000004bbc00 -- thread:0x60800107e4c0
503 Saw HELO/EHLO already