+1 vote

Hi, I am using Mail.dll with vb.net accessing gmail account.

It all works perfect, but when I move to amazon S3 instance I get an error: 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.

I have tried to open up ports on S3 instance as shown below: Was hoping you can help quick. Thanks.
TCP 995
RDP 3389
POP3 110
TCP 1025 - 1100
SMTPS 465
HTTP 80
TCP 21
HTTPS 443
SMTP 25

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Best answer

Default email ports are:

  • IMAP: 143; Implict SSL/TLS: 993
  • POP3: 110; Implict SSL/TLS: 995
  • SMTP: 587 or 25 **; Implict SSL/TLS: 465

SMTP (and port 25) was originally designed for transfer, not email submission.
So another port (587) was defined for clien email submission.

Gmail uses port

  • 465 (over SSL) for SMTP email submission,
  • 993 for IMAP (over SSL) and
  • 995 for POP3 (over SSL)

So it seems you are missing port 993 in your configuration.

References:

Default ports for email protocols
Gmail: IMAP, POP3, and SMTP settings

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