cannot send email from mobile phone if I'm not on Plusnet wifi

[#1]

I've got the same problem that many users have had, I can send email from the Gmail app on my mobile phone when I'm at home using wifi connected to Plusnet, but not when using mobile data or another wifi network. The answer always seems to be to authenticate the connection to the SMTP server but I've done that. I've used my accountname+mailbox name with the mailbox password, as accepted by Webmail, and various other permutations of username and password but I can't get it to work

Some posts mention the reputation of the IP address so, as suggested, I've turned airplane mode on for a few minutes to try to get a different IP address, but still can't get it to work. Is it possible to find out if it's the IP address causing the problem?

Are there any other suggestions to get this working?

Thanks.

[#2]

You must always change the SMTP settings when not on the PN network.

[#3]

What do you mean by "change the SMTP settings"? I've got them set to:

  Require sign-in  (Username and Password)

  relay.plus.net

  587

  STARTTLS

as recommended in How to set up Plusnet email | Help | Plusnet

[#4]

It's working today, I can send email from my mobile phone using mobile data.

I've no idea what's changed, I'm using the same settings that I've been trying for the past couple of days, when it didn't work.

[#5]

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@Gel wrote:

You must always change the SMTP settings when not on the PN network.

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Properly set up, that is not correct.

@ChrisK99 

It is not helpful that the Plusnet set up details suggest that there is no need to set up authentication credentials on the out going server.  Yes, one can get away with not being authenticated if connected via Plusnet, but as soon as one attempts to connect via a different network, things will not work (as you have found out).

The other thing which is unhelpful is that and email client is likely to report ALL connection failures as a username / password error, in spite of being given a clear indication of the issue.

The fact that this now works for you suggests either you have obtained a clean IP address and / or the too many failures lockout timer has expired after getting the credentials incorrect too often.