POP3 with outlook.office365.com gives timeout exception but works with IMAP

Question

We are using Rebex 2016 R3 POP3- 2.0.6198.0 version.
We are facing issue with POP3 whereas IMAP is able to connect to office365.

For pop3 facing a following exception:

A connection attempt failed because the connected party did not
properly respond after a period of time, or established connection
failed because connected host has failed to respond.

Our dummy code is: this is not production but just a simple test connection code.

var client = new Pop3();
client.Settings.SslAllowedVersions = TlsVersion.Any;
client.ValidatingCertificate += new EventHandler<SslCertificateValidationEventArgs>(ValidateCertificate);
client.Settings.SslAcceptAllCertificates = true;
client.Connect("outlook.office365.com", SslMode.Explicit);
client.Login("abcd@efg.onmicrosoft.com", "temp@123");

Do we missing anything for pop3?

Answer 1

The port number for Office365 POP3 is 995, which corresponds to SslMode.Implicit. Please, change the Connect method call to:

client.Connect("outlook.office365.com", SslMode.Implicit);

Comments

However, I am able to connect with both `SslMode.Explicit` and `SslMode.Implicit`.

---

Thanks for the reply,

well we have tried explicit and implicit options too. we have tried Rebex provided sample example for pop3_cs, this also gave same exception.  

to eliminate other possibilities i tried to login  with browser to check if it is accessible on the same machine, the account is accessible through web browser.  tried also on virtual machine where no antivirus is install.

I believe the sample application you have tried is similar to we have used right?

if it is working what steps should we follow to achieve it working.

---

Yes, I tried your code and our Pop3Browser_CS sample. Both works with Implicit and Explicit.

Can you please ensure, you have enabled outgoing connections to ports 110 and 995 on your firewall?
Are you able to telnet to that ports?

Run "cmd" and execute "telnet outlook.office365.com 110"
You should see "+OK The Microsoft Exchange POP3 service is ready."
Then type "QUIT"

For  "telnet outlook.office365.com 995" the terminal screen should be cleared.
Press 'CTRL+]'
Then type "QUIT"

If you are not able to telnet to that ports, POP3 will not work.
Please note, that IMAP access and Web access uses other ports, which are enabled on your firewall.