I haven't been following this discussion closely nor have I read through it. I am posting because iDevices were a constant problem for me when I was working with Mercury so I felt compelled to post. Please accept my apology if I repeat anything or suggest anything that has already been ruled out.
One recurring problem with iDevices was certificate handling. I had SSL enabled and used a Mercury generated self-signed certificate. Insuring that the iDevice trusted the certificate was paramount. Each time the certificate changed, there was no way to accept and trust the new certificate on an iDevice. The account had to be deleted and recreated, trusting the new certificate in the process.
Setting up credentials in iDevices isn't intuitive, requiring going into the Advanced area to enable/disable SSL and to set the port. The UI for setting up the SMTP server is different from the one for IMAP. iDevices will change the port to what it 'thinks' it should be. I never figured out what triggered it but I just reviewed the SMTP servers configured on my iPhone and found that two of five needed the password updated and both of them also needed the port changed (I don't do mail on my phone, just testing). An additional frustration, not specific to iDevices, is that each failed authentication attempt triggered a lockout (30 min?). I don't recall if this was on IMAP attempts but am certain that it was on SMTP attempts.
If the server name and the port is configured correctly on the iPhone you should see authentication failure records in the Mercury logs if those attempts are reaching Mercury but the credentials are incorrect. Also, if other devices (PC's, Android) can connect then there isn't any reason I can think of for an iDevice not to be able to connect other than mis-configuration on the device. Don't be shy about deleting an account or an SMTP server and starting from scratch.
FWIW, I had a network installation of Pegasus Mail running in conjunction with Mercury.
Pegasus Mail users (employees) were Mercury local users. Access from outside of the LAN was allowed to MercuryI (IMAP) and MercuryS (SMTP). MercuryI required authentication with local user credentials whereas MercuryS had its own credential list.
I haven't been following this discussion closely nor have I read through it. I am posting because iDevices were a constant problem for me when I was working with Mercury so I felt compelled to post. Please accept my apology if I repeat anything or suggest anything that has already been ruled out.
One recurring problem with iDevices was certificate handling. I had SSL enabled and used a Mercury generated self-signed certificate. Insuring that the iDevice trusted the certificate was paramount. Each time the certificate changed, there was no way to accept and trust the new certificate on an iDevice. The account had to be deleted and recreated, trusting the new certificate in the process.
Setting up credentials in iDevices isn't intuitive, requiring going into the Advanced area to enable/disable SSL and to set the port. The UI for setting up the SMTP server is different from the one for IMAP. iDevices will change the port to what it 'thinks' it should be. I never figured out what triggered it but I just reviewed the SMTP servers configured on my iPhone and found that two of five needed the password updated and both of them also needed the port changed (I don't do mail on my phone, just testing). An additional frustration, not specific to iDevices, is that each failed authentication attempt triggered a lockout (30 min?). I don't recall if this was on IMAP attempts but am certain that it was on SMTP attempts.
If the server name and the port is configured correctly on the iPhone you should see authentication failure records in the Mercury logs if those attempts are reaching Mercury but the credentials are incorrect. Also, if other devices (PC's, Android) can connect then there isn't any reason I can think of for an iDevice not to be able to connect other than mis-configuration on the device. Don't be shy about deleting an account or an SMTP server and starting from scratch.
FWIW, I had a network installation of Pegasus Mail running in conjunction with Mercury.
Pegasus Mail users (employees) were Mercury local users. Access from outside of the LAN was allowed to MercuryI (IMAP) and MercuryS (SMTP). MercuryI required authentication with local user credentials whereas MercuryS had its own credential list.