cannot send out emails (address rejected error)

[kenmurimi]

Hi All,

I have been using OTRS 2.4.7 for about one and a half years now.. recently i changed my ISP and so my SMTP settings changed, the earlier ISP used port 25 but for this new ISP they use port 587 for sending out the emails. on Core::Sendmail i have changed the SMTP address to the new address and also changed port to 587 (which are also the settings i am using on my Thunderbird to send emails and its working fine).
When i try to send emails from the helpdesk i get the following message

Message: Can't send to 'myemail@gmail.com': 550#5.1.0 Address rejected.
! Enable Net::SMTP debug for more info!

Traceback (32095):
Module: Kernel::System::Email::SMTP::Send (v1.25) Line: 131
Module: Kernel::System::Email::Send (v1.64.2.1) Line: 690
Module: Kernel::System::Ticket::Article::ArticleSend (v1.232.2.1) Line: 2027
Module: Kernel::Modules::AgentTicketCompose::Run (v1.81.2.4) Line: 424
Module: Kernel::System::Web::InterfaceAgent::Run (v1.43.2.1) Line: 819
Module: /opt/otrs/bin/cgi-bin/index.pl (v1.88) Line: 48

also on the logs it shows "550#5.1.0 Address rejected." on any attempt to send email notifications

any ideas to resolve this greatly appreciated
Thanks in advance
Kenmurimi

[crythias]

https://www.google.com/search?hl=en&q=5 ... s+rejected
General consensus is that the recipient domain is rejecting your email, which is what the error message said.
You wouldn't get this message if you were unable to send.

Check your SPF record in DNS to make sure you're not announcing that the new IP address is an invalid sender.