I get an error trying to use SMTP for email sending:Using Strato as an provider I have to use SSL/TLS. osTicket can't connect. I get the error:authentication failure ServerinformationenosTicket-Versionv1.9.12 (19292ad) —  Up to dateServer-SoftwareApache/2.2.31 (Unix)MySQL-Version5.5.47PHP-Version5.6.19

I guess this problem is related to the peer verification in php 5.6:https://github.com/osTicket/osTicket/issues/2628

If I cange the PHP version for my webspace to PHP 5.5.33 I get another error message:Failed to connect to smtp.strato.de

Well that's a different error that is not related to the peer verification issue. So far so good.In my environments all mail servers are using port 587 and there are no problems.However I tried for testing purposes a mail server that also uses port 465 and in this case it only works if you add "ssl://" before the server name:blankCan't say why this is necessary, but then it works (for me).By  the way: your provider also supports port 587, so you could use just port 587.

THX @[deleted] Both of your suggestions are working. I now use port 587.

@[deleted] Im glad that I could help you. You're welcome.

2 years later

I also had the exact same error:Failed to connect to **** And for whatever reason, when I put ssl://  in front of the SMTP server name it worked as well.I just also migrated my server one host to another as well.I spent around 2.5 hrs searching for this solution, so here are some keywords to help people find this solution:Keywords: "osticket server migration", "osticket error Invalid response code received from server", "osticket SMTP error"Thank you mfelber for your answer.

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