Office 365 email, send TO it from linux when port 25 blocked

Question

I use linux at home for many network and home automation tasks, and send myself email for events. My email is Office365 / Exchange Online (or whatever it's called this week) in a P1 (paid) account. This works fine using authenticated sends, but it results in two separate messages, one in sent mail, one in my in box.

This is annoying.

Is there any way to send via Postfix to Exchange Online that won't result in two copies?

Note my home uses Comcast and port 25 is blocked; I am familiar with and have set up IP specific receivers in Exchange Online, but as best I can tell that only works for port 25.

Setting up a separate VPN somewhere to avoid the port 25 block is possible but tedious.

Is there anyway to send authenticated mail to myself without the duplicate copy? Some header or postfix option?

Is there anyway to allow non-port-25 mail from a specific IP to Exchange Online?

Are there other alternatives?

Note I am NOT trying to send outbound email to other domains, this is only email to myself at my domains.

Linwood

Answer 1

Hi @Linwood,

Are you using port 587 instead of 25 to authenticate?

If port 25 is blocked, to me I am afraid on Exchange side there is no other method to send while not keep a copy in the sent items.

As direct send and Exchange Online connector methods both require port 25 to be opened.

Refer to Option 2 and Option 3 in this link:

How to set up a multifunction device or application to send email using Microsoft 365 or Office 365

On Outlook side, you may use some VBA scripts to automatically delete the messages in Sent Items.

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