Problems using Plusnet SMTP server from Gmail

[#1]

Hello,

I have my own domain name and I sometimes use Plusnet's SMTP server (relay.plus.net on port 587 using TLS with authentication) to send emails from Gmail. However, I frequently get the following error message (and the email is not delivered):

The response from the remote server was:

535 ...authentication rejected due to smtp auth user (<my-mailbox-username>) connecting from multiple places in the last hour, please contact support for more information

I presume that Gmail is connecting from a different IP address each time I send an email, and is hitting a limit.

Has anyone else experienced this? Can I really only send one email an hour? Is there any way around it?

For clarity, I only use Gmail to send emails like this when I'm away from home (i.e. not using my Plusnet broadband connection), I don't need to send many (but it'd be nice to be able to send more than one email per hour!), and I don't have any other SMTP server available.

Thanks in advance!

[#2]

Port 587 should use STARTTLS

If you are sending from your @gmail.com address … why are you not using Gmail’s SMTP server?

[#3]

Thanks for getting back to me!

In the Gmail "Send mail as" settings, the only security options for port 587 are TLS or SSL. TLS does work, aside from the issue that I have around a rate limit.

I'm sending from an email address on a domain that I own, not a Gmail address, hence having to use Plusnet's SMTP server. 🙂

EDIT: in case the security setting make a difference, I'll try port 465 with SSL as well.

EDIT 2: no joy changing the port and security type.