With update from 1.16.3 to 1.17 i have a lot of SMTP issues, that this wasn't before. My server is well configured and i can send Mails from other Websites without any trouble. I start to investigate some points and get different issues, but it seems that the most provider have a problem now to receive this mail via SMTP. In most cases i get a mail directly into spam folder.
First i get this issues:

or

I get a spam information from another mail with spam flag:
pts rule name description
0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was
blocked. See
http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block
for more information.
[URIs: fxxxxxxxe]
1.1 INVALID_DATE Invalid Date: header (not RFC 2822)
-0.2 BAYES_00 BODY: Bayes spam probability is 0 to 1%
[score: 0.0000]
2.0 HTML_IMAGE_ONLY_20 BODY: HTML: images with 1600-2000 bytes of
words
0.0 HTML_MESSAGE BODY: HTML included in message
0.6 INVALID_MSGID Message-Id is not valid, according to RFC 2822
The original message was not completely plain text, and may be unsafe to
open with some email clients; in particular, it may contain a virus,
or confirm that your address can receive spam. If you wish to view
it, it may be safer to save it to a file and open it with an editor.
That bad thing is at this point if my server send all the time bad mails the chance to get on a blacklist isn't far away.
One issue i found by myself. It's more then important that all user set date.timezone via php settings! You get also mail issue with RFC errors if this isn't set well for this domain you are using!!!
Additional information's:

After fixing php ini i get this error:
pts rule name description
0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was
blocked. See
http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block
for more information.
[URIs: ffg-braunschweig.de]
1.1 INVALID_DATE Invalid Date: header (not RFC 2822)
-0.2 BAYES_00 BODY: Bayes spam probability is 0 to 1%
[score: 0.0000]
2.0 HTML_IMAGE_ONLY_20 BODY: HTML: images with 1600-2000 bytes of
words
0.0 HTML_MESSAGE BODY: HTML included in message
0.6 INVALID_MSGID Message-Id is not valid, according to RFC 2822
-0.7 AWL AWL: Adjusted score from AWL reputation of From: address
The original message was not completely plain text, and may be unsafe to
open with some email clients; in particular, it may contain a virus,
or confirm that your address can receive spam. If you wish to view
it, it may be safer to save it to a file and open it with an editor.