Problems sending emails - blocked smtp port

[Anonymous]

I am on PAYG with an iPhone 5C.  

I can receive emails but cannot send via smtp.interdns.co.uk unless on wifi.  I have tried various ports, 25, 2525, and 587.

smtp.o2.uk on port 25 works occasionally.

any thoughts?  Any other ports to suggest?  

Am really fed up of the situation and going to move to another network if I can't get this sorted.

[MI5 · Accepted solution]

If using O2's smtp you need to untick use ssl and any other security verification as it doesn't use any.
If your providers smtp is blocked you need to speak to CS http://www.o2.co.uk/contactus

[Anonymous]

Thanks.

On o2's symptoms the ssl is unticked.
My provider's smtp is blocked - or was. I managed to send email using port 587, but that wasn't working a couple of days ago.

[MI5]

I use 465 with my Virgin email over O2's network OK.