Outbound email no longer working

Same problem for me.  Was working just fine for a long time and now get "authentication rejected" though I know I am using the right username and password.  It has not changed and I can still login to my account with the credentials.

Yes. There are other posts about the same issue, which it appears many people are experiencing. I got through with an agent at Comcast today, but they did not acknowledge the problem. (They told me I should contact the tech support of my email client.)

When I told them I would need to drop Comcast internet if they would not address the issue, they promptly transferred me to the billing department to cancel my Comcast internet account. It appears that they really had non concern whether I remained a customer or got the service they are supposed to provide.

It puts me in a bad situation because at the moment, the only real alternative at my address is CenturyLink, which is no better than Comcast and possibly worse. Fortunately, within 2 years, there will be at least 3 strong competitors in my area, so I won't have to live with CenturyLink forever and will certainly never have to go back to Comcast.

For anyone who's interested, I'd like to start an off-line discussion about ways we could financially damage Comcast to get their attention. If enough of us show interest, I think it's very doable.

after unchecking the security box for third party access, I cant send any mail from OUTLOOK. So that didnt help at all

Hello, after review of your uids it does not appear the third-party client access function is enabled. Please review steps in the link below to resolve your issue.

https://www.xfinity.com/support/articles/third-party-email-access

OK, I did it- now lets see what happens this afternoon. Unfortuneatly I am leaving for PHILA this afternoon at 3, but if it happens, it should happen by 1 or 2. fingers crossed. Thanks for the easy fix.

Janis

ok, this is the latest, now that I disable the check mark allowing third party access. I cant GET any mail. getting an error message that your email serv rejected your login, Verify usere name and password for acct. The server resonded ERRAUTH less secure auth dissabled

I too have begun noticing this. 

From my debug on postfix comcasts smtp gateway is rejecting plain / login authentication with a 

535 5.7.0 authentication rejected message. the smtp server is now offering a new xoauth2 mechanism however we are not provided with a way to obtain a client ID / secret to be able to make use of this authentication mechanism. This may be the death of using comcasts smtp servers for outbound email via postfix which is quite unfortunate as this has worked for many years for me and came in quite handy when I worked on SMTP servers for the government my home postfix was used to learn how to configure DKIM/DMARC/SPF. I have opened a new ticket with comcast regarding this very issue and hope to hear back from them soon. Unfortunately my entire street is having sporadic network issues on TOP of this recent publicly undocumented unannounced change to comcasts smtp servers I am NOT impressed with comcast as of late. 
Their customer support has absolutely NO bennefit to those who are technically sound and frequently results in calls lasting several hours just to get to a higher tier of support. 
This problem needs an answer from comcasts SMTP team, if this is in an effort to block those of us who have home email servers from being able to use them that would not surprise me. But the timing of this is just terrible many IT professionals are now working from home and need their home labs to be in a functioning state as they may not have access to a lab environment at work.

All,

I found a resolution to this. The comcast employee was not very thorough in his answer but it is the right answer. For those of us that have home email servers we may never login to our comcast email. 

We now need to login at least ONCE a year. Under the comcast web email account settings there is a security tab. We need to make sure that the 3rd party box is checked. After some testing I have concluded that email is now flowing as it should. Why this wasn't announced I have no clue. 

Upon my initial tests it appeared that comcast may be moving to xoauth2. This still may be the case but for now we are still able to use plain/login auth mechanisms in postfix as long as the above criteria are satisfied. Kind of a pain that we need to login once a year. But that is what we now must do.

Yep confirmed here as well.  The other day I signed into email which I never use and about a day later it started working again.   They should count sent mail authetications as keeping the account alive, otherwise we are going to have to login routinely.

cant this problem be fixed by Comcast.? Are they able to help you? I don't have all the expertise that you have and I dont know how i can fix this problem with Comcast and Outlook. I can send mail thru web mail, and Its Intermittent. I can send mail during the day until 1pm, then i cant until 7pm. Its the weirdest thing. I am hoping comcast can fix my problem.

thank you