SMTP problem : port 25 blocked by ISP

Hi,
I have a little problem to send mail with my SMTP server.
When I send a mail to Gmail, I get :
550-5.7.1 [my IP] The IP you're using to send email is not authorized 50-5.7.1 to send email directly to our servers.
Please use 550 5.7.1 the SMTP relay at your service provider instead.

I don't know if the problem comes from Gmail's servers or my ISP.
My ISP (Orange in France) blocks port 25 : we must use his SMTP server.
I have read that the users must change their configuration in Thunderbird/OE to use the port 587. Is this solution good to solve the problem with my server? In this case, where modify the Postfix configuration with ISPConfig ?

There is something weird too :
I can have 3 different sorts of IP : 81.xx.xx.xx, 86.xx.xx.xx or 90.xx.xx.xx
When I have an IP 86.xx.xx.xx, I can send mails but it doesn't work with an IP like 81 or 90.

What should I do to have my SMTP working?
Thanks for your help

 

You can configure your Postfix server to relay through your ISP's mail server: http://www.howtoforge.com/postfix_relaying_through_another_mailserver

In this case your users don'T have to change their email client configuration.

 

3 possible solutions are:

1) Use port 26 and have clients use it instead. I documented this a few posts back (just search by my user name).

2) Use port 587. Note that some ISP's are now doing the same thing with 587 as with 25 (your original problem, i mean).

3) They simply use their ISP's SMTP for outgoing mail.

It's totally up to you which one to use!

 

Hello,
Thank you for your answers and sorry to be late, I was on holiday
I will try on my next IP because for the moment that works. (My current IP is 86.xx..)

I just have a question, when I send mails to Hotmail, the first doesn't arrive but then it's ok. Do you have any idea?

 

I think you should contact the Hotmail support.

 

I've found the problem with the IPs.
I tried with ports 26 and 587 but it doesn't work.

Afterwards, I tried the 3 different sorts of IP on Senderbase (http://www.senderbase.org/) :
81.xx.. and 90.xx.. : poor quality (blocked)
and 86.xx.. : good.
So, it's why my mails were blocked with the different IPs.

I have to use my ISP SMTP server...

For Hotmail, I've found the problem too :
I use Thunderbird and when I send mail, the "A:" form is like that : Me <me@hotmail.com> but it must be like that "Me" <me@hotmail.com>.
I don't know why but in different cases that works.

I just modified my server with that command : postconf -e 'relayhost = smtp.wanadoo.fr' and it's working!