There are however moments where port 25 are also prohibited to use by your internet service provided and restrictions are made, so the only way to use SMTP are to use another server and port. If you have no other options, this is the method that we recommend you to use.
Be aware of the second relay, where port 587 is available. This is used, as a default plain text port, when the first option are unavailable for you - for example a restricted network, that do not allow communication through anything but standard ports.
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