This thread is from 2017, but I have the same problem with setting up my Comcast email account in aquamail. I'd prefer to set it up as an IMAP account, but could live with POP3 too.
I have used the pro version of AquaMail for many years and it's simply great. Even more surprised was I, when I tried hours to setup my Comcast.net account.
Every attempt failed with: "Outgoing mailserver (SMTP): authentification failure 535 ...authentification rejected"
Here's what I tried after giving it a shot with the fully automatic setup, which failed:
Add account - Internet Mail - email+password - manual - POP3 (I'd prefer to use IMAP though)
The server and authentification data from Comcast according to their website: (I am not allowed to post links) https ://connect.xfinity.com/faq/email.html#manualIMAP are:
imap.comcast.net
993 with SSL ON (or 143 with SSL ON)
smtp.comcast.net
587 (SMTP) (or 465 (SMTPS))
SSL Encryption checked
Authentication: Comcast email address and Password required
Opposed to what you recommended two posts earlier, Comcast recommends to use for POP3:
pop3.comcast.net
995 (POP3 With SSL) (or 110 (POP3 Without SSL))
You recommended mail@comcast.net, but that may have been a typo? I've also tried that, with no success.
However, I tried all possible combinations but did not succeed. It seems to be always the outgoing authentification which is rejected. I tried the full email and only the part before "@comcast.net" plus password and I tried the different authorisation settings like SASL PLAIN and SASL LOGIN. SASL CRAM-MD5 was completely rejected as a valid authorisation method, Comcast seems to not support that.
Incoming mail settings seem to be fine, just outgoing will not work.
Do you have any additional ideas?
Device: Samsung Galaxy S9+, most recent OS Adroid 9.0 Pie with Samsungs new UI, no root
AquaMail Pro Ver. 1.18.2-1413